>Easy, as well as the financial compensation, we give them time in lieu. Two hours callout in the middle of the night, two (paid) hours given back on their next working day, or whenever they prefer, subject to availability of other staff.

I didn't note this in my post above, but I always gave time-in-lieu for any late night activity. However, the thing that REALLY worked best was allowing the Engineers to prioritize reliability. I had to fight to make it happen, but going from nightly to every couple months volumes was worth it.