Can you use the Microsoft File Server Migration Toolkit (FSMT) to migrate shares between servers in different forests?

A. Yes, if the required trusts are in place between the domains of the source and target servers to allow the user running the tool to be a member of the local Administrators group on both servers. Be aware that SID conversion (which is the process in which the user's old SID from the source domain is replaced with the new SID in the target domain) doesn't occur between domains. If a domain is being retired and SIDs on the permissions need to be translated, you should migrate the source server to the new domain using the ADMT tool with SID translation prior to running the FSMT or use the SubInACL tool. After data and shares are migrated, the ACLs will remain unchanged and the permissions are maintained and will still function thanks to the existence of the trust between the servers' domains