Encountered a variant of this OoB exploit performed by a Sinclair in a real match (ID 47687583).
It seems like the invisible walls do not extend to the corners of most of the roofs adjacent to the base structures, and, while some characters such as doorman and Sinclair have means of then teleporting out, several spots allow for players to simply slide off of mantling and clip through one of the invisible barriers.
Attached several of the spots where people can gain access to the roofs not already addressed above.
Also attached demo of clipping OoB without the use of any character specific abilities (I do not believe this is due to size of character model, as I have accomplished this with several characters including Talon and Bebop as well).