Damaged units will heal 2hp per turn when resting in another AI's land if you have open borders. This is especially handy for naval units, as they cannot heal in open waters. I've upgraded units within allied city state territory, although I haven't had a chance to try it in an open border situation.
Last edited by pdxsean; September 27, 2010 at 18:09. Reason: further benefits
What's up, hot dog?