If they really want to align incentives it makes sense to switch to time-of-use based pricing like electricity providers have done. Since most of the cost is building infrastructure to support peak traffic, suggesting that consumers shift their usage pattern to be off-peak would be a notable cost benefit.

The obvious problem besides the added complexity for users is that I suspect there is relatively little "background" traffic usage. Almost all of it is people watching streaming video or interactive downloads. I doubt things like software updates that can be scheduled add up to much.

It would be interesting though. I wonder if it would lead to services promoting their download options more (example auto-download likely videos every morning).