So I ISO modded CoD WaW on my 360 and was wondering if I'm able to transfer that modded version of the game to my Xbox One, or am I only able to play it on my 360?
If the game was digital content then no. The license will be on your account and able to be downloaded on the xbox one through the store.
If the disc is able to pass security checks without modded drive flash or hot swapping then it might be possible. (But I would highly doubt any burnt disc will pass)
If this was possible by now there would already be many threads on how to do it. So I would say nope not possible.