Although I don't have the reference handy, I do seem to rememberthat the Foxbat was indeed capable of mach 3 flight.
However, seeing as how the performance of the blackbird is for the most part still classified AFAIK, and given that the blackbird is capable of flying at 80K + i sincerely doubt that the Mig25 would ever have had even the remotest chance of flying wing to wing with it.
cheers,
RTR