Living in the D.C. area, I can only speak for experience but Verizon seems to operate two groups of techs.

One as you said are in-house and unionized, these guys seem to mostly handle the apartment complexes and large installments.

The other group handles regular houses, or off-one jobs when the market is exploding.

I've spoken to techs on both sides, and they both confirmed with mild disdain the existence of the other group.

Just an anecdote.