Would he explain how the system works for allocating positions for recruiting. I will assume that you are talking about positions for occupations and not recruiting positions for CFRC/Ds. Every year a Strategic Intake Plan (SIP) is developed by NDHQ through input from the various players (element commands, managing authorities, etc.) to determine how many positions will be needed for each military occupation for that FY and then it is determined from where those numbers will come from (direct entry, CT, OT, UTPNCM, ROTP, etc.). Then recruiting is given the numbers that they need to enrol for that FY to meet the SIP.
It seems to me that when an individual comes in they can apply for whatever trade they want, realizing of course that the mob sends you where it wants/needs you in the end. An applicant can apply for any trade they want if they meet the application requirements for those trades and yes if they are enrolled they are usually sent where they are needed in that particular occupation not where they would like to go.