Our house was built about 10 years ago and all the phone lines were wired with CAT 5e. I was thinking of changing over all the phone jacks to ethernet and switching over to ethernet phones like the Cisco SPA502G. Are these compatible with the Shaw home phone service or do I have to keep the antiquated RJ11 jacks?
No, not directly. Shaw provides a device that interfaces with your existing home wiring infrastructure so it works like the POTS service you'd get from Telus. (which is a bit more of an advantage as you can now use any cheap off the shelf phone that you can buy anywhere).
The SPA502G will work with a Cisco PBX, or a VoIP phone service that uses SIP (like FreePhoneLine, VoIP.ms) but not for the residential phone service that Shaw provides.