What I really want is an extension tube for my telephoto lens. (70-200mm Canon) I have an opportunity to purchase a number of macro tubes. Will those also work with the telephoto lens?
Yup, they'll work - tubes should work* with any lens, even a reversed one for extreme macro.
But the magnification is relative to the focal length - so adding 50mm of extension tubes to 200mm doesn't get you super close, show stopping macro shots. Using it at the 70mm end will produce higher magnification shots (although probably not 1:1), but less working distance.
*Obviously if they don't have electrical contacts you'll lose a lot of auto stuff, but that's not relevant to the focal length issue.
A few months ago, I used tubes with my Canon 135/2.8 to get a shot I couldn't get with anything else in my bag, including a 50/1.4 which is theoretically "better" to use with tubes.
The shortest tube I had on the 50 compressed DoF so much and reduced the far focus distance so much that I simply couldn't get the shot. The subject was too big to fit in the frame once it was in focus, and I would have had to close down the aperture too much for the available light. (Raising ISO wasn't an option here.)
All I really needed for this shot is to reduce the near focus limit a bit so I could get a little closer than the lens would allow on its own.
So, yes. Tubes FTW.