Intervals would have to be exercise specific to benefit any particular exercise. Doing intervals whilst swimming, running or stair climbing would help your conditioning but they would not give you the maximum possible benefit.

That being said, doing intervals on a good facsimile of a bike like a spinning bike or a bike using a resistance unit should be very close to what you want. If you are more comfortable going all out when you are not on the road, you will probably do better sort of simulating the bike that way. I probably will not be quite as good as exercising to the same intensity on a bike. But if you feel more comfortable on your simulation and exercise more intensely, you might get a better result.

good luck

Pat