Probably brushless, so most likley the motor itself will handle any voltage you care to throw at it...but the cotnroller probably won't, with out some upgrades to it. It might do 72V without mods, maybe--depends on the FETs, caps, and the input stuff for the low-voltage regulators/etc.
One possible issue is that the heat buildup inside the motor might be too much, given that it likely has very little airflow over it inside the velo shell. It might require cooling modifications to sustain the power levels needed for 30MPH, though with the velo shell those requirements may be dramatically lower than on a regular 'bent bike/trike. You might have to put a thermal sensor in there to keep an eye on it at first, to see how it reacts, and add cooling if necessary.
Cooling could be as simple as holes in the cover, or filling the hub partially with oil (ATF, actually), or as complex as ducted air or pumped liquid cooling.
My guess is it will work fine at the power levels needed without any of that, as long as you can get airflow across the casing itself, but you may have to experiment to be certain.
BTW, if you ever get tired of the velo, I'd love to get my hands on one....