Older fixtures dont carry a Listed tempurature rating, so I think technically, if the old wires are still in order and have not been subject to overloading over the years that making the connection is okay. If your hanging a chandelier of course, there is plenty of room to disapate further damage from heat. The problem I still have is the new fixture or chandelier probably still carries a 75C or 90C temp. rating and therefore not approvable. The contractor that makes that connection is more than likely the responsible party in the event of electrical failure.
The reason I Put this question out there is so many times this connection of new fixtures to old wires is what is asked of contractors by dwelling owners with the foremost issue for the owners is not incurring further costs on the project.
To me customers requiring connection to old wires requires an explanation of the Codes, a proper quote for necessary rewiring with the fixture changes, and walk.
