The Condition CHECK FILE in the Postconditions of a BS2000 Job cannot access tape files. This is not foreseen and will not be changed.
https://us.v-cdn.net/5019921/uploads/editor/y9/qj9pcv021khr.png" width="930">
Instead of using post conditions, you can use a OS Job with a command like
/FSTAT :B:$SA.T.ADR.H05-SPLAE.SPLAUS.100117
If it ends with ENDED_OK, the file exists.