Anything is possible.  It is just a matter of transferring the forum data from one set of tables to the others.  However, there will certainly be many complexities involved with this as far as the differing table schemas, UserIds and user information, and so on.  This is not a small or easy task.  I would suggest studying the two table schemas and user information data stores and come up with a plan before you begin anything.  Red Gate has some good tools for assisting you in this process.

As Will mentioned it is a complicated process, but it can be done.

If you are looking to contract it out I might be able to help you but I can tell you that it will be an expensive process as it is VERY tedious and takes a lot of time to research, implement, test and validate.