You could run 911 calls through a cellular gateway using a few different methods depending on your PABX. Historically it was not at all uncommon to run most cal

You could run 911 calls through a cellular gateway using a few different methods depending on your PABX. Historically it was not at all uncommon to run most calls over VoIP but use an ISDN or analog line specifically for emergency calls. But I wouldn't really recommend it, there's a lot of complexity with GSM e911 that is different from the complexity with non-cellular e911. I'm only familiar with the US regulatory regime, not the Canadian one, but VoIP operations are usually required to take very specific measures towards proper handling of 911 calls, particularly since the recent US legislation wrt central notification of 911 calls from multi-tenant facilities. So there are reasons to stay pretty close to the letter of the law.