Ack! Forum ate my post! Ok, so here it is, best as I can from memory... :)
That's an excellent question; I have no idea what precipitated it. It was before the legislative session, so it couldn't have been the campus carry bill. Maybe the shootings last year. Perhaps the UA has been talking to DHS like Malco. lol
As for the signs, they are posted on UA property at the outer corners of campus (Razorback/Maple, Razorback/MLK, etc.) I haven't checked EVERY outside corner, but all the ones I've seen have them. The design is a gun with a slash above the text "Carrying a handgun or other weapon is prohibited on campus".
I wouldn't imagine it applies to the streets themselves if you're just driving through, of course. A gray area would be the metered parking around campus. They are UA-controlled, but possibly part of the street, so I don't know what rules apply. Of course, if you are a student/employee, the UA rules will apply with respect to your enrollment/employment, regardless of whether it is actually illegal or not.