I think it depends on what programmes you've applied. I do hear that some programmes only start sending out rejections slightly before 15/Apr. Maybe one possible solution is to check their website and find out when they will finalise all the applications. And email them if it has been a couple of days after their proposed date.
I'm almost in the same boat... Still haven't got any decisions from CMU, which is supposed to come out before 1/Mar. I think I would email them if receiving no emails this week... sigh Good luck to all