This thread doesn't really make any sense at all to me. Why are you even telling Comcast about your wireless or your security cameras? How would that even come up as part of scheduling a service installation?
Buy a Surfboard 6141, plug it into your wall, and open internet explorer. The activation process will automatically pop up because it's an unregistered MAC. It's completely automated, you put in your name, address, and Comcast account number, click the little box to activate your new modem and click the little box to deactivate the old one. Drop the old one off at any Comcast office within 30 days so you don't get charged for it. If you're a network engineer i'm pretty sure you can handle the process of activating the modem.
You never need to talk to a Comcast rep or anything outside of returning the modem. When you call to upgrade to the 105 plan you just tell them you have your own top of the line Docsis 3.0 modem and do not rent one from them. They go "oh, ok, then you dont need an installation." They up your bill and flip the switch for the service. The end.
The *only* time I could see that $250 install fee is if they *had* to do an installation that required running a new line to your house because there wasn't one where you wanted it (or at all), because that's a PITA and does cost a lot of time/money for a tech to do.
Seriously, just politely tell the rep you're in IT and know what's up. That's usually one of the first things I mention when I have to talk to them and they're usually pretty thankful they can skip most of the scripted BS and we can hash out the call in 5 minutes instead of a long and painful hour of troubleshooting. Always very friendly and helpful.