'Beyond the Meter'
Just is not inspected. Ever. The only code enforcer of is Petroleos Mexicanos with their 1366 pages of stiffly inspected and regularly reviewed regulations for new construction gasolineras newer than 2002. This is a 100% paint by the numbers qualification - stiffer than any USA building code inspection I have even seen in the USA (excepting hospitals).
80% of the homes down here have twin black, or red and black wires leading from the mufa. White? Sometimes but a bad percentage have L1 and L0 reversed.
CFE makes sure a black and a galvanized wire extends to the mufa. They are strict about mufa to meter wire gauge and color code, but from there anything goes. I just left a house that had 12 gauge TWIN BLACK wires feeding the entire house. And a 30-amp TWIN breaker inside the house. The 12-gauge wires were run in black tubing buried in 2" of dirt and gravel.
Only gringo built homes I mean SUPERVISED BUILT, have any semblance of code. When I designed and built a 40 Kw tres hilo (three phase) system for Duran Trucking in Tecate 17-years ago I had a dragged out fight with Fernando, to code four conductors and green ground all receptacles.
Suggestion: Remove nose from book. Move to reality of what the eyeballs verify.
Mexico is THE LAND of rules and regulations. 99% of which are utilized to find infracciones for multas, fines. But electrical codes are like unicorns, sasquatch and a USA balanced budget. Utter pipe dreams.
Know Before You Go, is useful for RV connections. If a person knows in advance what to expect they can deal with it in a rational planned manner. Bringing a box of specification grade receptacles will minimize plug fires. Getting a Y shaped piece of rebar made-up will support hookup cables.
Wanna blow the mind of an RV park owner? Bring boxes of Ideal wire nuts. Two sizes. Red and Blue. He won't have a clue - show him how they work. Bigger parks can use medium size KEARNEY NUTS - copper clamps for major neutral and line ties.
What's supposed to be, is always trumped by WHAT IS
And Mexico is the land of WHAT IS.