Rogers has come through with a $15/month BlackBerry Internet Service plan. It includes unlimited email (including attachments) and use of PIN messaging for BlackBerry Messenger. (Update: You’ll probably have to call Customer Service for this to be added. The number is 1-888-ROGERS1; make sure you specifically mention “BlackBerry” when prompted.)
The plan’s supposed to only be available for Pearl users; I need other instant messaging capabilities on my personal device, however, so I can’t test out whether a Pearl is actually required to receive this plan.
Another new lower-cost plan added to the customer service/support site is the addition of a $25/month 4MB data plan, which is more in the range of a light email and instant messenger user. It matches similar offerings from Bell and Telus in the BlackBerry push email space.
Thanks to Howard Forums for the updated info.