Okay, so I found some stuff after looking for "hydraulic pedestals", but the offerings are fiendishly expensive, and not really intended for the original use; you'd still have to built something around them.
Your best option would be to make something yourself, or get someone who can to do it for you. You just need a basic telescopic hydraulic cylinder to do the lifting. You could probably do missile-silo style doors using a mechanical system operated as the platform moves upwards, or a pair of cylinders connected to the same circuit (so they operate at the same time or slightly before). Obviously timing is crucial on when such doors open
The easier alternative, which is what I've seen with the show-off coolers, is to have basically two circular surfaces one above the other, with a gap large enough to fit the Mac Pro between them (well, a bit more than that), joined together with some kind of supports (metal rods would work well). This way when the unit is closed the top surface is flush with your desk/counter, and when raised the bottom surface is flush, revealing the Mac Pro.
I've seen a pretty cool alternative you can use to an air compressor for operate the hydraulics; since you shouldn't need a huge amount of pressure to lift a new Mac Pro, you basically have a reservoir flush with the top of the desk/counter, with a cylindrical "plug" inside that has a handle on top. The plug has pins on it that correspond to notches in the reservoir such that when you rotate the plug it locks into place. Basically with the plug locked in the upper position, flush with the desk surface, the reservoir is full of air and the telescopic cylinder isn't', so the Mac Pro would be in the low position. When you rotate the plug and push it down, it forces air form the reservoir into the telescopic cylinder, raising the Mac Pro into the high position, you then lock the plug in place to keep it there. Since you'd need to go fully bespoke to get this done then it's an option if you don't want to have to use a compressor to do it, but such a manual system would need to be done very professionally.
