Austinlaing, in terms of the assessment center my best advice would be to get a good nights sleep beforehand. It is a mentally challenging day but honestly was a lot of fun. Trying to prepare would almost be doing yourself a disservice - we really don't know exactly what is being looked for in a candidate so just give everything a fair crack and hopefully you'll be fine.
Maggie Island, it is my understanding that so far only a handful of people have been offered a spot on an upcoming Enroute course. There have been no tower spots offered yet. At the assessment center in February they were definitely recruiting for both roles.
On the day we were told that AirServices was hoping to run two enroute courses and a tower course this year however they stressed that nothing had been locked in so I would not be banking on anything.