Earlier this year, PUC President Michael Peevey told Edison they had to provide the information by Feb. 28, 2013.
Now Edison has to "prepare testimony" based on preliminary engineering studies of options for running transmission lines underground by Dec. 3.
Moreover, Edison has to provide the PUC a rate recovery proposal and a detailed report describing the cost and scope of the materials and service contracts, and the associated timing required for such contracts, that are required to install an underground transmission option for the section of the Tehachapi Renewable Transmission Project, according to PUC documents.
The new PUC order came on Nov. 15.
The $2.1 billion Tehachapi project aims to carry wind-generated electricity from Kern County to the Los Angeles Basin.
Edison already has started extending the towers about five miles into the right-of-way.
But city officials and the grassroots group Hope for the Hills have advocated building the project underground.
Chino Hills officials have spent more than $2 million battling Edison in a lawsuit for two years insisting the right-of-way is too narrow for the proposed 198-foot towers and that it causes safety hazards.