Hello,
AFAIK, the answer is NO. I don't find any such migration guide from SAP - but u can wait for others to reply.
BTW, IMO, u have to do development from scratch, so there is no reusability of previously developed mappings and all (becoz there are quite a few differences in XSDs of Seeburger and B2BADDONs)
Below link will give u some pointers for B2B addons.
Seeburger or Crossgate or B2B Addons?
Thanks
Amit Srivastava