Yes, it looks like OSM. There are small roads that I've mapped that are only on OSM, and are present on these maps. The data from OSM is from april 2010 (based on "The road added to OSM on $DATE1 is on these appple tiles, but the the road added on $DATE2 isn't")
And yes, it looks like they've been using it for a while, no-one noticed till now.
No, the same tile sets are used in iPhoto for OS X (part of the iLife suite) and some people claim they're used in Aperture (another photo editor but I've not used it).
Where they have used it, they used it as hint as to where a photo was taken. The more detailed info panes still use google's maps.
Apple have actually been using this tile set for a while (it's used in the slide show mode of the current version of iPhoto for OS X).