Used Bio TA a good few times and never had 100% success.
OT8 on block is great and works pretty much all of the time but Tarmac is like an oil sponge, it just keeps coming. Got to the point where I'm sure all the oil that is going to go has gone but always a level of shading, especially to the core of the spill.
Best to be realistic when talking to client.
Re-colouring is an option but not actually gone down that route as yet.