Ah- imagination required, sorry.
It should fit just fine, may just have to fettle the rear shock tower a little for clearance. The 1518 is only about 3-5mm longer than the 1515 based on the comparsion of the 1520/1518/1512 in the photo above- if you take a look at the birdseye views of the BL erevo you get a good idea of how much space is available- one of the little brace thingies might need a notch cut into it, but nothing drastic realy:
http://www.traxxas.com/products/elec...op-chassis.jpg
Im sure dimensions will be posted when the new motors are put up for sale in the next few days or so- check the CC website at that time.