Psst Silas, looks as though a few more of my assumptions were in fact perfectly correct:

http://www.guardian.co.uk/world/2011/jun/15/pakistan-arrests-five-spying-cia

"The CIA hideout in Abbottabad was set up some time after last August, when the CIA began to suspect Bin Laden could be hiding in the area, less than a mile from a major Pakistani military facility.

Watching from behind mirrored glass, CIA officials used telephoto lenses and infra-red imaging equipment to establish a "pattern of life" inside the compound and eavesdropped on voices inside. But they never conclusively identified Bin Laden."