There's a whole 'village' of condo type units in an area west of Portland that are like Aaron describes. There's a huge gable vent and they're plunked right in front of it. I've done probably a half dozen of these over the last couple years. Some actually have some installed and some are just setup for it. I can always tell by the super-huge attic access hatch.

These places are so close together I don't there is anywhere outdoors to put the compressors. The buildings are all pretty much 06 construction and newer and appearanty the AHJ is okay with it.