You may be confused as to what bootcamp does.
It allows you to boot up into windows, it also provides the drivers needed to access the hardware in windows.
That means its not some sort of middleware communicating between windows and OSX.
You can however share files between the two partitions by formatting the xp partition as FAT. There is a product called macdrive that perports to read/write HFS+ drives in windows giving you the ability to read and right to your OSX partition. I have no experience with this app so I cannot say if its good or not.
Mike