I had the same experience recently in PHL. (I believe it was 1589 to DTW on 1/31 scheduled 9:05 a.m.) We had to wait for a "police escort to accompany the plane" because it had to be "towed across an active runway".

Makes no sense to me.

Makes even less sense to me now that I hear it wasn't an isolated incident.

Where are they towing the planes "from"?