Not collecting debts owed to a Govt body is a hidden subsidy.
I'm always cautious about the S word - remember FoE and their "£10bn subsidy to aviation" claim, which they won't actually back up when scrutinised.
But yes - I see what you are saying, you are into the murky world of unpublished accounts.
Also, I hadn't realised the extent of Catalan ownership, so fair enough.