No, you can be let go at any time, it is a zero hours contract, although as long as you mantain the standard you will get some hours.
However......
As many people have found ej have over recruited massive amounts of FO's over the last two years (something we were told they would not do) so the flexicrew guys who were getting 900 hours a year are now finding that these hours are dropping off considerably. Over the winter plenty of people were flying 10-20 hours a month. That works out to about £1000 gross with a standby thrown in. That's tough to live on. Yes, but you fly loads in the summer I hear you say, great, a possible 100 hours in the summer months works out at circa 4.5k gross a month for about 4 months. Enough to break even from the incremental debt you got into over the winter and then it's back into the lean winter season.
Basically throw in another 5k loan at least for additional living expenses in the first year of flying and forget about paying back any of the loan which will be rapidly growing through accumulated interest.
Although with expansion rapidly slowing down at ej I would have thought that the odds of getting into a job are increasingly slim.
I would wait to see what kind of deal the MPL guys get when they get on the line.
Seeing as how they can only work for ej I can't see them being on anything like the hourly rate currently 'enjoyed' by flexicrew pilots.
The risk/reward ratio skyrocketed towards risk over the last 2 years. Anyone who signs up for a course of flying training now without a very clear exit strategy if all goes belly up and who simply hopes that they will get a job is, in my humble opinion, crazy.