I do believe it is the northern part of the ACC, rather than the southern part, most vulnerable to Big Ten first initiatives. The ACC made a couple of big mistakes with expansion: not taking WVU, and accepting ND w/o all fb. Pitt & Louisville, with the ACC, are good fits for the scheme. The ACC should have waited, maybe, in pursing the upper northeast corridor (Syracuse, BC). Whether such would have kept Maryland, hard to say with the monetary enticements. But, it could have impacted Big Ten thinking as to strategy and aggressiveness.
I'd like to think that if the ACC would not have gotten weak in the knees over Miami and had taken the Hurricanes either ahead of FSU or with FSU at the same time, things would have gone so differently than they are now. Maybe the VT thing would have still happened, but the ACC is a sloppy expander, even if unpredictable.
How the ACC expanded impacted how the Big East began to see itself, which affected the ACC and right back at the Big East. Both are not ideally where they want to be.
As for BC, it's a better fit for the B1G than some think. BC also fits the profile of the last two acquisitions: neither come in with deep ties or relationships to many schools and carry around with it a good urban market, even if they don't own Boston. Plus, until the ND situation is fully settled and figured out, BC is in the same boat as UMD was and now Pitt is when it comes to "sharing" Notre Dame...possibly at BC's expense.
So if BC goes, UConn's safer off.