[CAN use ok] AT&T Prepaid - $28USD per line with 8GB data each line usable in Canada (after multiline disc for 5 lines)
With 5 lines at 8 GB per line, it comes out to total $140USD, or $28USD per line ($36.53 CAD at today's exch rate). It is possible to get a small-business plan for up to 10 lines that would bring the average cost down even further to $24 USD each line. It's possible to have people at different amounts of data on a multi-line prepaid plan. Obviously, this also includes data in the USA and Mexico.
With 5 lines, a 8GB plan is $28 USD per line ($36.53 CAD)
With 5 lines, an unlimited data plan (22GB -> Throttle) is $43 USD per line ($56.08 CAD)
Also currently comes with a $50 USD VISA prepaid card for buying a new device or SIM kit online, on a $35+ USD prepaid plan, and making payments for 90 days..
Multi-line discount page (still has the old language requiring >50% of usage not in Canada):
Full credit to /u/ShadeezBlack who posted to PersonalFinanceCanada.