I don't know the answer, but I can't think of a reason this would be a no-no, as long as the switches are rated for that voltage. Are you talking about having a wall-mounted receptacle outlet powered by 240 volts with a 3-way arrangement for switching that outlet? Here again, so long as the receptacle is the correct type for that voltage, so that nobody tries to plug in a standard lamp, I think it should be OK.
What is the specific application you have in mind?
Even though running a 240V lighting 3-way is irregular, making a 240V hookup would be no different than a standard 3-way wiring diagram with the exception of the opposite phase leg as a common return to each luminaire lamping rated for a 240V load. There is no grounded neutral return circuit. The travelers switch phase leg A and are isolated from the common phase leg B return in the same 14-3 cable.
Switching one phase on the travelers is proof of the pudding to isolate Phase B as the return in that circuit to the other side of the 2 pole breaker. Not practical for the lighting of modern LED low voltage lamping.