I took a look at this garage yesterday. It's a little weird. The vehicle entrance is on Oliver, opposite the entrance to Franktuary. There is no pedestrian access on that side of the building however, and the ramps clearly says "no pedestrians."
Pedestrian access is via the Piatt Place Sales office lobby, on Fifth Avenue. It's pretty upscale, so I suspect all bikes come in and out via the Oliver Ramps.
The bike racks are in the standard Parking Authority "off in a corner" location. They are located at end of the car ramps, but the incline of the ramps make them pretty much invisible from passersby on Oliver Street. There appears to be a staff office in the general vicinity, and it has a window overlooking the bike rack area, but I don't get the sense that there is anyone there full time, or anything.
Bottom line, I think this garage is the most fortresslike garage I've ever seen in Pittsburgh -- it's sort of hard to figure out how to get in or get out. I like that element. The bike rack location is not ideal, but it is far better than some I have seen, and is not "in the public view" the way many racks are. I saw four bikes parked there yesterday, with room for about 4 more.
Go for it, but be careful, and lock your bike securely. If you hear anything as you use the racks that seem to confirm that there are no problems at this location, or that there are problems at this location, let us know, huh?