If you were killing them on-top of sardons tower then yes they will spawn there, on other towers e.g. swamp and deadwood the guild holding the tower will spawn inside the tower not by the flag.
But here is a list of the towers and their spawn point for the tower holders just incase:
-York, inside the tent
-Castle, in the flag room
-Deadwood, second floor under the flag level door
-Sardons, on the flag level
-Swamp, In the water in the first room as you enter the tower