I've never met a Comcast sales person who was able to operate at the level you're talking about. I think you would do better with a smaller company.
I think you were also unrealistic if not disingenuous about lives put at risk. Alarms do not require more than 300 baud.
Comcast would actually like to sell individual internet service for each of the five units. That's what they're geared to do. You're not going to get that very high speed rate for that ridiculously low price and fan it out to five domiciles. They would offer that for a single home and the users that could be expected in a single home, or maybe a small business but I think they would charge a business more. I pay Comcast more for a very small business at a lower rate.
I think realistically the fiber connections you're talking about at the data rate you request in the privilege of fanning out to five domiciles should cost about $2400 per month.
I get the complaint about wires on the outside etc. But who are you expecting to do that work? If you expect Comcast and their competitors to do that as part of their standard installation, you're asking for tens of thousands of dollars of work, and if that is to be the standard then everyone must pay much more than today. Nobody wants that, and most folks don't care about the current standard of installation. If this mattered enough to your homeowners association, they could pay for it.