GSM to HSPA?

Hi, I just had a few questions and hopefully someone can help me out. I don't think these have been answered anywhere else.

I'm currently on a Telus contract and with their new HSPA network I'm pretty sure their new phones require a sim card? If I were to bring a phone that was previously used on a GSM network would I be able to insert Telus' sim card and would it work?

Also, Currently where I live there is no HSPA network but I go back to Montreal to study so I'm in Quebec for the majority of the year, where there is an HSPA network. I've done a device swap before and I know the costs. Would I be able to do a device swap from an HSPA phone to a CDMA phone and then back again?

Thanks for any info!

Here's the deal. If I remember right, Telus is CDMA and HSPA. So, if a phone is a GSM phone and HSPA you'll get HSPA, but not CDMA on Telus. Essentailly, if you do not have a 3G signal, you'll have no service at all with a GSM/HSPA combination. If you buy a Telus phone that has HSPA frequencies, you're gold.

Ok, so I understand most of that. One other question (haha sorry), Are there phones that are GSM/HSPA or is a simple GSM phone okay?

Basically I'm asking because I want to know if I can take my brother's phone and use it. He's with Rogers (GSM) and getting a new phone and I'm with Telus (CDMA/HSPA). If it's possible, I would buy the HSPA sim card with Telus and insert it into his old phone.

Thanks for answering some of my other questions though, that was helpful.

With the Rodgers phone, if it's only a GSM phone, no, you will not be able to use it. If it is a GSM/HSPA phone, then yes, you will so long as you have a 3G signal.