They have had a call out rota since the Lex Harvey days it's only compulsory in the areas they can't get enough engineers to cover it. Example if they have a team of ten engineers and no one wants to cover the call out then it's split between all of them, which would be a week in every 10 on call. Plus they are paid about 200 a week just for being on call and it used to be 4 hours time and a half for being called out. I'd do it if I was still there