He didn't waste any time responding to Brian Mulroney's claims. Karlheinz Schreiber says there's one way to tell whether it's Mulroney or him who is telling the truth: look at the documentary evidence and call other witnesses. He says there's a lot to be learned from bank records, hotel receipts, etc.
Schreiber disputes two cornerstones of Mulroney's story. He denies Mulroney's claim that their business deal was made only after BMPM left office. And he denies that Mulroney earned the money by lobbying heads of state at the international level. Schreiber maintains there wasn't even anything, any product, to promote.
I expect the next time the ethics committee hears from Karlheinz Schreiber - that is if the Tories don't get rid of him to cover their asses - they can expect to receive a pile of documents contradicting Mulroney's claims.
So far, the best analysis of this bucket of deceit and duplicity I've read is Andrew Coyne's. If you haven't read it, take a look: