I have no experience with it whatsoever, but I do try to follow what goes on in the linux kernel over time..
The Linux Media folks have been working on things in the linux kernel for years that might help you? Lookup linux cec and the media controller api??
One thing I could think of is if the shaw STB has a firewire interface?
I am pretty sure Mythtv has been used by some folks to interface with their Cable STB using firewire (IEEE 1394) for those cable systems that allow it in their STB SW.
I don't have any satellite subscriptions so I have no motivation. I have only used Mythtv
with PC based ATSC and DVB-S(2) tuners.
DB8E/VHF Yagi rotor FM Bandstop ap-8700 preamp 8way split LG lcd.