No offense intended, but whether or not there was an oversight when they wrote the law is irrelevant. It is still a fact that there is no specific law governing the transport of an unloaded handgun by the holder of an LTC-A. Don is correct.
The topic of this entire thread (and the point Don made) is transport. Storage is not transport.
I once again have to disagree, the purpose of this thread is the OP wanted to know how to transport the handguns. He didn't want the academic mental gymnastics of the Mass law. Like Len 2a said, Don's reply is dangerous and could get a new LTC holder in a lot of trouble.
Also, read 131(L).