The employment contract just states the terms and conditions of flying for easyJet, and states that you are bound to fly for them after completing training - as long as you meet their standards... To be honest, if you are wanting to apply to other airlines, and do not have your eyes set directly on easyJet, after the 18 months/2 years, would it not be best to consider Whitetail? The scheme is designed for those that specifically want to work and fly for easyJet for whatever reason, and in the interview they specifically ask "why easyJet"...
Think the different routes allow and encourage different types of people to apply. I.e. Those don't have the A-Level results/degree, but still would easily make a very successful easyJet First Officer...Perhaps call CTC/L3 mate for more info?