Presumably it includes all the normal "master socket" functions and electronics as well, so adding your own NTE5A as an internal distribution point could actually cause problems.
It definitely needs some sort of internal central connection point that, ideally, matches the physical interface of the NTE5A on the "user" side.
Doesn't sound 100% thought through into the "real world" does it?
Sorry to drag up this old thread, but I have fitted a few external NTE now and also the customer internal wiring. I agree that the first internal socket should include a test socket and be able to accept an SSFP (filter faceplate) to provide a good DSL connection.
My solution is to use a NTE-5, with the components removed (so as not to double master the line) and a link fitted to allow connection of the ring line from the external NTE (the ring line is filtered at the external NTE) This allows the test socket to operate as it should, with any phone, and avoids the possibility of an additional master showing as a fault if the internal wiring is tested from the external NTE test socket.
While this will not be accepted as the demacation point, it does help with Broadband and in the installations I have done the run from the external NTE to the first socket is less than a metre, often directly behind it on the inside, so there is little chance of this being damaged leading to no dial tone at the NTE-5 test socket, but a dial tone at the external NTE.