I don't think anything in Apple's product line without Gigabit Ethernet autosenses. This Apple knowledge article base backs me up on that. Remember of course that only one end of the pair has to support auto-mdix for it to work. Thus if you've plugged, say, a G4 Powerbook into G3 doorstop, then it worked because the newer machine could do it.
There are a few hubs/switches that run at 100mb that can auto-MDIX, but it's a vendor-specific feature (HP Procurve 10/100 network switches newer then 2003 or so do, for instance.). Auto-MDIX *is* part of the GigE specification.