There's been a lot of discussion before about whether T-Mobile's international blackberry plan includes non-email data or not, with inconsistent answers from T-Mobile and inconsistent experiences by users.
I tried it last month, and as of October 2007, I can confirm that T-Mobile's unlimited international email plan does not
include other data. It may once have been included, but if so, they've changed their system since then and can now successfully separate them, at least for BIS (I cannot speak to BES, and it might be different).
I was in Canada for a couple days; I called them up to turn on the $20/month plan, and then I loaded a couple of web pages. I got the bill and there's an itemized per-kilobyte charge in addition to the $1.33 for two days of the prorated plan.