Not sure how the recruitment process works for ab initios, I applied for experienced ATC position and for me the process was as follows:
Apply online, submit resume'
Get asked to do online testing
Pass online testing --> do a face to face interview with an ATC line manager, someone from HR and someone from the college (simultaneously)
Get told you passed interview and have to go in and do some more (verification) testing (including spacial awareness, this is supposed to be done in person not at home but due to some technological shortfalls at the place i was supposed to do it, I end up having to do it at home anyway)
Do an interview with the manager and ALM of where they think they are going to send you.
Give you an offer. (or not, still know some buddies who havent gotten one)
Getting the medical isnt cheap. It will probably cost you around 500 bucks all up, ASA will reimburse you though if they decide to employ you.
So for me I was more or less told I would have a job straight after the interview (was told that I interviewed quite well etc) for me this is when I should have started my medical, I would have had it well before my start date, as it was I was still running around trying to get it whilst I was at the college)
I am not sure they afford the same courtesy to ab initios as they did to me (letting me start the college etc before I had my medical)