The Generation Interconnection Agreement specifies how a facility procures its station service.  MISO does not require transmission service for station service.  It is the generation owner’s responsibility to work with the appropriate entity on a contract for obtaining the station service they require.

If a local utility exerts their right to charge the facility retail rates for station service, the generation owner cannot use Schedule 20. 

Schedule 20 is optional.  If the generation owner chooses to use Schedule 20, they still pay the hourly LMP for the energy consumed.  Schedule 20 nets the facilities monthly output to determine if transmission charges should apply.  If the facility is net negative for the month and using remote self-supply, the generation owner will be charged non-firm point-to-point rates for the net negative amount.  If the facility is net negative and using on-site self-supply or third-party supply, MISO notifies the Local Balancing Authority or third-party supplier respectively, of the net negative amount and any charges are settled amongst the parties outside of MISO.

BPM 014 - Station Power

Note Wind Farms:
Schedule 20 evaluates the wind farm for transmission service charges if they are net negative for the month.  In other words, if they withdrawal more energy than they inject over the entire month. 
If they are set up as On-Site Self-Supply or Third-Party Supply, and are net negative for the month, MISO notifies the Load Serving Entity (LSE), Local Balancing Authority (LBA) and generation facility of the net negative volume and any billing for that is subject to whatever contracts they have in place with those entities.  There are no transmission charges from MISO.
If they are set up as Remote Self-Supply and are net negative for the month, MISO will bill them for non-firm point-to-point service for the net negative volume.