Ah. Okay, downloading KrashNburne and IntenCity multiplayer now, probably have better luck seeing something other than zero in that first column. Main problem here is "the underlying technology" is allegedly there between TS12 and TS Mac multiplayer, but when I hosted a session he couldn't see it, when he hosted a session I couldn't see it.
Straight answer to simple question - are TS12 multiplayer and TS Mac multiplayer INTENDED to be compatible or not? Whether it's actually possible or not remains to be seen, whether the underlying technology theoretically exists for compatibility is not the question, the question is: Were TS12 multiplayer and TS Mac multiplayer designed (and tested!) with mutual compatibility in mind or not?