You'll find that different companies have been able to negotiate different requirements for their particular operation. Though 400 hrs TT including 40 hrs PIC in multi IFR is quite a common basic requirement. There are some (Scotland Air Charter springs to mind) that require just 700 hrs TT. Also there are plenty of small operations out there not on a AOC and so may not have any min requirements as such (I'm thinking of stuff like flying businessmen around in their private company twin, aerial survey work, ferrying etc)
Duir hits on a good point. It strikes me that in some respects the career route many of us end up following is all backwards, i.e going straight onto the the very demanding single pilot IFR ops where potential for cocks ups is high and then later moving on to airlines. Wouldn't it be more sensible to start off all low hours guys in the nice safe environment of a big jet in an aircraft that won't let you make any big mistakes and having the extra safety net of an experienced captain sitting next to you ?
Good luck