Can you replicate ASE 12.5.3 to MSSQL ASE 15.7 using Rep Server 12.6?

Customer would like to migrate from ASE 12.5.3 on Compaq Tru64 to MSSQL ASE 15.7 using Replication Server 12.6. What are some of the issues to perform this migration? What version of MSSQL is supported with RS12.6? Any help here would be appreciated. Thanks.