First of all, I seriouisly DOUBT the NBA has people dedicated to catch account sharers. They would first have to detect two different ips (which could be played off as a couple diff computers in the house with different games going), ESP with NBA's lack of LP security last year I doubt they will suspend or cancel any accouts
IPs can be traced by location, so if one of those IPs traces to Texas and the other Pennslyvania, it's pretty obvious they're not from the same house.
I'm not speculating on whether the NBA does this, I'm just telling you what's not only technically feasible but pretty easy to do.
As Baretta used to say, don't do the crime, if you can't do the time.