Hi Ocean:
1. Teksavvy does provide service to Montreal
2. Their 911 service is just as reliable as any other VOIP or VOIP-esque service, which is essentially on par with POTS.
3. In regards to throttling, you are subjected to the same "Internet Traffic Management" system that the rest of the Bell network is subjected to. Teksavvy, like ALL OTHER DSL providers in Montreal, are leasing Bell's lines. However, Teksavvy is known to use different DSLAMs than BCE which allow workarounds via SLPPP linux software which can circumvent Bell's "Internet Traffic Management" system; this workaround has not been known to work with Bell's DSLAMs.
BOTTOM LINE: If you do not care about customer service and technical support, Bell incontestably offers the best deal in respects to pricing, bandwidth allowance, speed (best DSL), and reliability (not UBER shared like cable [Videotron]). Unless you want the breakneck speeds of cable (up to 50 Mbps), which again can slow to a halt a peak times, go with Bell DSL.
** IMPORTANT SPEED NOTE: ALL resold Bell DSL is limited to 5 Mbps (or it was last I checked) whereas service directly from BCE is available at up to 16 Mbps.