I don't know - but I don't think I'd want to use it! Maybe someone else will have a clearer idea.

It is possible to experience some of the effects of rat poison if in contact with it. Warfarin etc is a blood thinning compound commonly used in rat poison and the dose in rat poisons is much higher than that used for humans. I personally would not use it any place that has an animal or a human food chain. Compost is in that chain?

I've found that rats only start nesting in the compost heap for two reasons:
1. Putting too much food waste into it, especially meat.
2. Leaving the heap for too long without turning it and getting it to heat up.

Turning the heap is a real chore, and I don't enjoy it, but not only will you get rid of your rats if you keep disturbing them, but you will get far better compost in the long run. Mix in more carboniferous material like torn newspaper or straw as you do so.
If you are concerned about "Elf and Safety" (I never bother, having built dams and mud pies out of cowpats in my infancy, I think I'm immune to everything!) be aware that rats can and do carry Weil's Disease and that you can pick this up through scratches and other wounds if handling contaminated compost.

Depends which compounds the rat poison being used contains - in the past, it was always coumarin (warfarin like compounds) but these days, other things are used too. It also depends how long it will be before you use the compost - if its left for months and we have rain, most of what's in there will wash out, assuming you have an open heap rather than one contained in a compost bin. Even so, I wouldn't use it on beds for veggie growing though.

As the compost is likely to get a lot of handling I would not put any sort of poison in it.