I did ask Verizon, but they were initially unable to tell me anything.
After making several more calls and having the issue escalated, they finally told me that while roaming in Saskatchewan with a CDMA device, there will be no 3G, only 1xRTT.
It is odd, as while the Verizon phone was in Saskatoon it wasn't getting any data connection at all, not even 1xRTT, whereas when it was in Nova Scotia it worked fine with 3G and falling back to 1xRTT when 3G was weak (which was very rare). So, no idea why it's not working for data in SK, even though it's in a 1xRTT coverage area.
We've just chalked it up to SK being a wireless wasteland, and resigned ourselves to using WiFi when at the place we're staying. Can't wait to get back to Nova Scotia and the modern world!