edit: Okay, the page says "Special Opti-Wiz™ based board". What the heck does that mean?
It means that it is different than the stock Opti-Wiz. The TurboTwist 2 required a different component to be installed than the one on the stock Opti-Wiz. The stock Opti-Wiz has been tested extensively (Thanks Kremmit!) with a good number of optical arcade devices, so I did not wish to alter the original design. This has no bearing on the TT2's ability to be used with other optical interfaces (I understand that it has been done successfully), only that the TT2 requires a special Opti-Wiz.
Anyone wanting to connect a TB and TT2 to the same device should use the Master version of the TT2 and connect the trackball to the interface supplied with it. However, given the issues with the Z-axis under Windows and the fact that MAME no longer adjusts for it, I find myself recommending that folks just use a separate interface for each unit. That way, the TT2 can use the X-Axis, the TB can use X and Y, and MAME can keep track of them as MOUSEx.
RandyT