Can I use my iPhone 5 sim card on the iPhone 6?

So I currently have an iPhone 5 with a 2 year contract for about $35 a month. I'm upgrading to an iPhone 6, can I take the sim card from the 5 and put it in the 6?
I heard that Telus (the phone company I'm with, as well as Rogers, Bell, etc) is making all iPhone 6 users have a plan that has to be $80 or higher. If this is true, is it possible to still have my $35 dollar plan on the iPhone 6 somehow?

I'm in Toronto, Canada if it makes a difference.

No.

Yes. Both the iPhone 5 variants and the 6 variants use a Nano SIM. Just make sure the new iPhone is sim free and unlocked from all networks.

Yes you could swap the SIMs as they both use nanoSIMs. As far as the plan thing, no clue.