In my experience this depends on the entry-level you're targeting. I can tell as a post-MBA hire, there is a sign-on bonus, but it's actually done in a way that it lowers your tuition (so you don't get the cash). It was all very standard, and not negotiable. In general, at the more junior levels of MBB consulting, the rules are not very extendable, so there is little room for negotiation. This was my experience in Paris and London anyway. You can check the temperature, but don't push too hard for it, because in the broader scheme of things, a sign-on bonus doesn't represent all that much (and it can reflect poorly on you if you insist too much).