Gavin,
You WON'T be able to use your Telus phone in Europe, as Telus uses CDMA technology (as opposed to the "world standard" GSM). Rogers & Fido use GSM but you would need to be on a contract plan to use international roaming. You have a few options.
Check with Telus regarding their roaming plans. They might be able to provide you with a Motorola A840 for your trip (rental?), which works on both cell formats. There's also the Blackberry 8830. I don't have information on what roaming costs they have negotiated with the GSM carriers in Europe? Again, check with Telus.
I've been traveling with a Rogers GSM phone for several years, and it's worked well so far. You'll probably find that the voice rates are somewhat "pricey" ($2 per minute incoming, $1 outgoing in country, varies with country). I normally use text to keep the costs down and stay in touch with family at home (you can text to any cell network).
If you need any more details, send a PM.
Cheers!