Doesn't the BTN have a pricing policy that says cable systems in states where teams are situated pay a lot more than those that don't? That policy is effectively predicated on the schools being "State U" and thus being able to attract viewers far beyond the alumni base. BC, like most private schools*, can't bring the type of viewer interest to justify the high rate. 90% of sports fans in Massachusetts couldn't care less about BC. In fact, I'll bet that if the B1G took UConn, they'd have far more MA cable systems sign up to pay 10 cents per month (or whatever the actual figure is for non-represented states) than would sign up if they took BC and wanted $1 per month. Add in the fact that far more in CT would be willing to pay the higher rate (even though it is a smaller state) because UConn is "State U" and they would probably make more on subscriber fees while also having a much broader advertiser base and more exposure for the schools.
* Northwestern is a fantastic private school, but if they are getting higher rates in Illinois it's because of the Illini, not the Wildcats.