Castellon as a location is relatively new to the aircraft scrapping business, one of a number of newer locations that have appeared in recent times to deal with the upsurge of withdrawn airliners. BA had only just started using that location, with in the past BA using Victorville [USA] Kemble and Newquay [England] St Athan [Wales] and Teruel [Spain]
The oxygen system should [hopefully] have been turned off at the bottles but maybe someone missed the two crew bottles that are in a different location to all the passenger bottles or forgot to depressurise the crew system?