As the current service department for Nagra, and former service tech for dCS, Musical Fidelity, NAD, Arcam McIntosh Labs and several others, I guarantee that none of those companies ever allowed schematics to be distributed to customers or non-authorized service companies.
Most manufacturers require signing a non-disclosure before sending the tech their manuals.
I totally agree with this philosophy; keeps all the hard earned R&D costs in house.