More than once I did fly over the strats (enemy as well as friendly) and found the amount of damage visible at the factory not matching with the status on the clipboard.
Today I did a test in an online arne I created with standard MA settings. I took down a refinery to 0% (City still at 100%) and waited. Afterabout 30 minutes the factory started to regenerate - but only to 2%. After more than one hour since I took the refinery down, I visually checked the area - as one might expect, everything was fully back up, but the status on clipboard was still reading: 2%. Even now, about 90 minutes later, it still is.
Edit: Leaving the arena and logging back in does update the strats display to the correct value.