The article linked below mentions a 10 kV line on steel poles from Santa Maria Regla to Pachuca constructed together with the hydroelectric plant in 1895. Few hundred meters from the Presa San Antonio you can find these poles, which belong to a minor line running towards Pachuca. I don't know if these were the original poles from this power line. Only few of them still exist, most poles already were replaced by modern concrete poles.

https://reference.insulators.info/publications/view/?id=3414&h0=1895