Patience is the operative word as Canada Post begins the process of getting mail service up and running again after the government passed back-to-work legislation on the weekend to end nearly a month of labour woes.

Locked out June 14 after 12 days of rotating strikes, some of the about 48,000 postal workers returned to their jobs Monday after Bill C-6 received royal assent Sunday evening. The bill imposing a labour contract on the Canadian Union of Postal Workers was passed by the Senate following a 58-hour filibuster in the House led by the opposition New Democrats.

In Halifax, managers and workers at the main Canada Post mail sorting plant returned to work late Monday afternoon after picketers earlier had refused to let anyone inside without a police escort.

More than 60 people were on the picket line on Almon Street as of 8:30 a.m. local time.

Police told the managers they would be escorted into the Almon Street plant if they wanted, but managers decided to leave around 9:30 a.m.

The union members said the managers would be allowed to return to work once the afternoon shift started at 4 p.m

The U.S. Postal Service said Monday it was accepting mail bound for Canada. The post office said that mail held since the work stoppage began is being released and transported to Canada in stages.

It said there will be some delays in service due to the large volume of mail that was being held.

But on Monday morning, there were lingering effects of the dispute, as picket signs were still sprouting up in areas of the country — including outside mail sorting facilities in Halifax and Montreal — and workers protested the new legislation in other ways.

Jon Hamilton, a Canada Post spokesman in Ottawa, told CBC News on Monday morning that he recognizes there's still a "smattering" of pickets.

He expects they will come down later in the day after the bill received royal assent about 8:45 p.m. ET Sunday, because legislation will be fully in effect 24 hours later.

Hamilton also said it's too soon to tell how the strike and lockout will affect Canada Post revenues, given that many people turned to courier services and online avenues to get their deliveries out and pay bills.

"We're going to have to see when the dust settles how much business we lost," he said.

Staff will be at 'full complement'

For consumers, the big question is: "When will I start getting my mail?"

Canada Post says mailboxes that were sealed shut are opening Monday, so Canadians can start dropping in mail. Any mail already in the system will be handled as a priority, said Hamilton.

"We're going to work with our full staff complement, starting on the afternoon shift today [Monday]," he said, reiterating Canada Post's announcement that mail delivery should resume Tuesday, but it may require some patience to get everything back in full gear.

"The sooner people get [their mail] in the system better. We will continue to move it through," Hamilton said. "But we have 500 depots, 20 plants, thousands of trucks — so it will take a little while to get our full logistics system up and running. We're being cautious and don't expect people to think we can immediately turn it back on and get everything up to speed."

CUPW president Denis Lemelin told senators on the weekend that the union would respect the legislation if it passed, although it raises difficulties for employees, who weren't consulted about the provisions.

On Monday, Lemelin told CBC that while workers are committed to doing their jobs — "First thing, we want to deliver the mail" — the union plans to look closely at the new legislation "and analyze it competently and how we can challenge it or use some part of it to really try to make it work our way."

The new law imposes a four-year contract on the workers, specifies pay increases and leaves other disputed issues to binding arbitration. It also provides union members with slightly lower wages than the last offer from the post office.

Lemelin said the union's board will analyze how to approach the arbitration process, taking its cues from who will be appointed arbitrator.

"Our collective agreement is a complicated one, and we need someone who understands labour relations and someone who can see exactly what is happening here at Canada Post."

Talks between the two sides collapsed late Wednesday, and a final half-hour discussion Saturday morning failed to bring any resolution.

“The legislation provides for enormous financial penalties for individuals and union representatives in the case of defiance,” CUPW said in a statement Sunday. “We believe that this government would use any excuse to destroy the union should we defy the legislation, and we will not give them any opportunity to do so.”

In Vancouver, where union members picketed outside the main post office on Monday morning, local union president Robert Mulvin said workers planned a rally and march downtown at noon to protest the way the contract was imposed.

"There's no mediation or arbitration, which is unprecedented in terms of how we've done collective bargaining in the past."

B.C. Federation of Labour president Jim Sinclair, meanwhile, predicted the situation gaining heat.

"I could see this getting more confrontational going forward. Workers didn't join unions to go backwards."

Eric Gauthier, president of the Charlottetown local of CUPW, said Canada Post can expect workers to continue to fight for their rights.

"People are already talking about a general strike. But, we'll fight — work to rule. If they want a fight for the next four years, they've definitely got one."

Gauthier said workers will "just do everything properly. Exactly what's in the book. Take your time and take your rest periods. Don't go above and beyond, which most postal workers do from day to day to get the mail out because we take pride in our jobs."

With files from The Canadian Press and The Associated Press