Get on the Clue Train
Get on board, FH1100.
I am far from being a tilt-rotor proponent but your question apparently comes from ignorance of information that's been published in the trade press for about the last 25 years or so concerning the tilt-rotor's construction, i.e., the XV-15, the XV-22, and the whatever-it-is-now-609.
To wit: the two engines input to their respective prop-rotor gearboxes, and there is a cross-drive shaft connecting those two gearboxes. So, in the event of an engine failure scenario, which would include a loss of engine oil pressure, the failed engine would be shut down and the remaining engine would drive both prop-rotors through the connecting driveshaft...similarly to the way that both fore and aft rotors in a CH-47 are driven by the drive shaft that connects the combining transmission to the forward transmission.
As somebody else in this thread tried to point out to you, what this means is that a TR with one engine failed would be in the same situation as any other twin engine airplane with one powerplant failed, i.e., proceeding to a landing site on partial power, as such multiengine vehicles are designed to do...with the exception that the tiltrotor won't have the problem of asymmetric thrust/drag resulting from one failed plant, such as a King Air or other twin turboprop plane would have.
And yes, there is a sprag clutch mechanism that declutches the powerplant from the respective transmission when transmission speed exceeds plant speed, i.e., if that powerplant should fail.
Now, if you want to raise a serious question, by all means ask what should happen if one of the prop-rotor gearboxes should lose lubrication; but that is an entirely different situation than the engine oil pressure scenario you are thinking of.
Look, you can be against the tiltrotor all you want (again, I am myself), but try to make your objections from a position of knowledge rather than ignorance. Because as it is you're making our side look bad.