CBI sources said an FIR was filed following its preliminary enquiry when it found enough material to proceed with a regular case against Maran and BSNL officials -- the then CGM K Bramhanathan and MP Veluswami.
The agency which had registered the enquiry into allegations in 2011 had wrapped up its probe in July.
Maran could not be reached for reaction either over the phone or text messages.
The sources said these 323 residential lines were allegedly in the name of BSNL General Manager connecting the Boat House residence of Maran with the office of Sun TV through a dedicated underground cable during his tenure as Telecom Minister.
The probe had started in 2011, nearly four years after getting complaints that a 'virtual' telephone exchange was allegedly set-up at the then Telecom Minister's for facilitating data transfer from Sun TV.
The agency had recommended action to the then Telecom Secretary in 2007 but the department allegedly did not give its nod in the case, they said.
Finally, CBI had filed a preliminary inquiry in the case in 2011, they said.
The sources said these lines were not ordinary telephone lines but costly ISDN, capable of carrying huge data thus facilitating faster transmission of TV news and programmes across the globe.
CBI in its report to the Telecom Secretary had alleged that these lines were for use of large commercial enterprises to meet special needs such as video conferencing or transmission of huge volume of digital data for which heavy fee is charged but Sun TV got it for free.