An analysis by a group of civil society organizations claimed that some decrees signed by President Enrique Peña Nieto earlier this month open the doors to the privatization of several water sources.
The line will be 21km long and have 16 stations. Construction is 77% complete.
Brazil's next administration will need to attract the private sector for infrastructure projects given the government's fiscal challenges, says Alexandre Garcia, an infrastructure analyst at Fitch Ratings.
The Brazilian construction group is in talks with Ashmore to sign up to a bond issue.
The government signed multiple deals with the private sector to boost the economy, while an official set banks and cooperatives on equal footing in terms of credit cards.
The anaerobic digestion facility in Naucalpan, Mexico state, will treat the municipality's organic waste and generate electric power.