I’ve learned some more about the Rogers Wireless “Pay As You Go” service:

• They don’t support roaming to the U.S. at all. There’s no way to request this, no way to turn it on. My phone here in New Hampshire currently shows T-Mobile and AT&T GSM networks, but I can’t join them.
• Similarly, you can’t roam on a Pay As You Go plan anywhere else outside of Canada. This in contrast to my experiences with the Croatian VIPme service that I was able to use in Slovenia, Italy and the U.K. with no problem.
• Calls are billed by the minute not by the second. In other words, a 3:04 call costs $1.32 (4 x $0.33) not $1.01.