The normal procedure is to post you as far away from where you want to go as possible
(except for several lucky ones like me who got exactly what they wanted).
The posting system seems to be a combination of an enormous roulette wheel and Chaos theory
In all seriousness you can make it known what you want and you might get it, but "business need" is what will determine it at the end of the day. You'll get a posting where it is needed and where *they* reckon you will do well at with very little consultation; unless things have changed.