Grid connection

Access to gas transmission networks for fossil natural gas is guaranteed in Spain and there are Government regulations and access tariffs (Royal Decree 949/2001 regulating the access of third parties to gas installations and establishing an integrated economic system in the natural gas sector).  Specific requirements for biomethane to be injected can be found in the above mentioned protocol PD-01 

Refusal of grid access

When failing to meet the above mentioned requirements

System usage fees (non-discrimination?)

See Royal Decree 949/2001 for the baseline. Last (at June 2012) update of the fees can be found in the 'Orden IET/849/2012', of 26 April 2012:

Connection cost burden sharing

Costs covered by the 3rd party willing to inject into the grid.