If IoW is 3rd rail based, then it should work Watford-Euston. If its 4th rail based, then it’ll only work Kilburn High Road - Bushey, as thats the extent of 4th rail on the DC line. This should work for both the 483 & 484. Best way to see if it’ll work is spawn it in, and see if you can set a valid destination.
Then it says unreachable location this is not a valid location. But it may seem like it is. I wonder if that a bug.
Then I think it won’t work. The 1972 will only work over Bushey-Kilburn High Road, if you try sending it to Watford it says its an unreachable destination.