Do Indian classical music labels pay accompanists a share of a release?

At KalaSudha, yes. On a concert KalaSudha records, KalaSudha pays each accompanist for the concert itself, and when the recording is released the accompanists share in the royalty alongside the main artist. Tanpura players are paid a fee for the recording. Every performer on the release is named in its PPL registration with the full line-up.