Thank you for the explanation. The loc_ref  tag definition on the main ref page (https://wiki.openstreetmap.org/wiki/Key:ref) says for use on "local reference numbers or codes". Since this ref system is specific to Mendoza, how do you feel about using the loc_ref tag for these and restoring the ref tags to their original version? This would help distinguish the local ref system from the one more widely used across the country in my opinion. 

Let me know what you think, and if you would like any help making updates!