You can configure an individual dataset to be accessed via Fileshare, or by a specific Fileshare server overriding the one specified in the Default Allocated Dataset Location.
Go to the FCT page for the file (in ESMAC, select Start L on the Resources dropdown list, then click FCT, then click Details by the file), and then:
(Because JCL does not need transactional VSAM access, the catalog page does not have an explicit Fileshare Server field as the FCT entry does. However, simply including the Fileshare server name in the path in the Physical File field does as well.)
In a similar way, you can specify that an extrapartition transient data file is to be accessed via Fileshare, by naming a Fileshare server on the file's DCT page in ESMAC. Also, the SIT page in ESMAC has four fields where you can specify that temporary storage queues (recoverable and non-recoverable) and intrapartition transient data files (recoverable and non-recoverable) are to be accessed via Fileshare.