The question is why those two though?
It's something I've pondered as well. Soundwave I can understand... biggest of the toys they were planing to sell as "Decepticons", he might have considered as a "leader" character at some point.
But why Prowl of all the Diaclone cars. Police car equals Authori-tah?
(Although I do think you have to squint more to make Soundwave's face into the symbol than Prowl)