Hi EML,
I applied last year and just missed out so waiting to re-apply next week.
When I applied, I waited about a month before I got a response from my initial application to do an online test. When I did the online test, had an email the next morning to book a phone interview and at the end of the interview was told I was successful and would be contacted for an assessment which happened a couple of months later. If you're successful at the assessment day then nobody really knows, but back then about a couple of weeks seemed to be the go.
From what I understand, whether you pic En-Rout or Tower doesn't seem to concern them so much. I guess it would depend on their operational requirements and possibly your performance during the assessment may demonstrate you have greater aptitude for one over the other which they might consider.
I don't know much about what's covered in the course, but anything on weather and air law would be a good start. Maybe Bob Tait CPL Weather which pilots study and the AIP and CAR for law.