I find this very odd, as Tamaimo(Santiago del Teide) has an ambulance crew on stand-by 24/7. People sleep in the Centro Medico. That is why they shut down the Cruz Roja, as it was not needed anymore. Also, like the fire brigade, ambulances are not confined to their area .
I think this is a misunderstanding somewhere along the way. I have asked my OH(who as regulars know is Canarian) and he confirms if Santiago del Teide's ambulance is out on call, then Guia De Isora's would be sent automatically, or the next nearest.