Emergency calls on US GSM cell phone?

We have seen lots of Green Angels on roads other than cuotas. I once read an article that said every mile of the major highways is supposed to be covered twice per day by a Green Angel. And you can always call 078 if you have a cell and are in reach of service. I also read they now have more than 2,000 service vehicles. They also have some camper trailers and there was a program to escort groups of RVs around the country with a Green Angel camping with them. We saw a Green Angel escort with a group from Quebec at the Teotihuacan RV park a few years ago. They are all supposed to be able to speak English. We hired a retired Green Angel to drive us around Mexico City a few years ago. I have been seeing Green Angels around Mexico since my first trip in 1971 - before cuotas. I know there used to be a more extensive website about them but have been unable to find it now. I did find a couple more things about them. If you need you can download Google Translate and almost any foreign language will be translated - sort of - not perfect.

http://eleconomista.com.mx/industrias/2014/01/11/angeles-verdes-ayudaron-mas-1-millon-turistas-2013

http://eleconomista.com.mx/industrias/2014/09/12/angeles-verdes-refuerzan-servicio-carreteras

http://eleconomista.com.mx/angeles-verdes