What about doing hill repeats? Say something like:

5km x 4km x 3km x 2km x 1km
or
3 x 3km
etc.

And hill repeats ARE being trained, do you have to give out max effort each time or can to spin up the hill? Keeping in mind that the down part is the recovery. Once you get to the bottom of the hill, you turn around and start back up again.