I would prepare for some questioning at immigration in GRU, so get there with time to spare.Bring both RG and CPF and the expired passport. If there are no restrictions on the persons right to travel from the Brazilian side, it should go through.
Now, the problem comes when the person returns to Brazil and enters on a foreign passport. If he just arrives and forgets all about it, we will have an visa overstay situation on the foreign passport.
My suggestion would be to apply for a Brazilian new passport on an emergency basis (last minute business meeting abroad is always a good reason, if you can get a letter from a company). Passports can be issued in 24 hours at the airports on this basis.
As mentioned above, the Federal Police has a very good data base nowadays and they will be able to see this irregularity on their computers.