Hello Huyoen,
I sent my application through Xpresspost without the paid option of signature. I sent it to the P.O. Box address. Although some consider Xpresspost as a courier service, I read that it is still Canada Post, so they have access to the P.O. Box and should be able to deliver it.
Update: my application was not rerouted and was delivered on January 30th, 2019.
Anyway, I called IRCC 2 weeks ago and they didn't have any news on the extension of the pilot project. I was told that spouses could still apply for the OWP after January 31, 2019, and it just wouldn't take only 4 months to receive it. I keep checking both websites (PR sponsorship and OWP) and the instructions are the same (that you can mail the 2 applications together). None of these websites mentions any deadline to submit these 2 applications together, which makes me think that they should at least accept applications posted until the date that the websites show such instructions.
