Graynomad:
If the library doesn't support controlling the EN pin (it should, we all want to save power :)) then I'll cross that bridge when I come to it.
It does use the enable pin. But, right now as soon as CAN and CAN2 are instantiated they immediately enable the transceiver and leave it enabled. So, the library basically assumes you're using a 234 chip. This has been accurate for the most part. Since they're instantiated automatically for you this means that the current library forces the relevant pins to be CAN and enables the transceiver forever. Of course, not everyone wants this behavior so in the future it should be possible to turn off the canbus hardware if required. This is not hard to do at all. I think that the default behavior of automatically turning everything on is still the way to go. If you don't want that you can not include the library in which case it won't do that. 
But, yes, on the to-do list is being able to disable and re-enable the hardware.