No, it doesn't work that way, unfortunately. The Step 1 tool creates in addition to the transit lines and stops, a SQLite database containing the GTFS schedules and other information necessary for the transit evaluator to work later. If this database doesn't get created, then the Step 2 tool will fail, and you won't be able to use the transit evaluator in the network dataset either because it won't be able to look up the schedules. Unfortunately, the tool was designed explicitly and exclusively for use with GTFS data...