Indeed, it would seem most manufacturer's use roughly the same size steel tubing for their roller frames, the exception being kreitler. Alu frames vary quite a bit more i think.

I'm waitting for my nashbar's to arrive, but assuming the tubing width is rougly the same i worked out where i'd have to drill the 2 attachment holes for my tacx mag unit so i could use the same belt.

This is just calculated though, these values might change slightly when i actually start putting things together.
One thing to note, that the value 393 or 395mm is the stretched value of the small (355mm) tacx speedmatic belt. The whole reason i did all this work is so that i could use the default belt that comes with the mag unit, however you could also use a 15.5" micro V belt, which can usualy be special ordered from a belt supplier (check any local industrial park) for around 5$.