I would think that JW lawyers that are part of the Bethel "family" would not be compensated any differently than other Bethelites. If they were lawyers before coming to Bethel, they would most likely retain their business.
Would they charge the WTS? Do electricians, carpenters, etc., charge the WTS for services rendered on building KHs and assembly halls? I don't think so.
Even when a JW needs a lawyer due to a legal situation coming out of a "preaching" situation, the WTS has sent a local JW lawyer to assist at no cost to the JW involved. That lawyer volunteers their time just like JW electricians do on "builds."
The WTS does contract out legal business to non-JW firms and those firms would charge the WTS for services rendered.
I do wonder what happens if a JW lawyer works for a non-JW firm, if they can donate their time? Many law firms do a certain percentage of pro bono work.
Blondie