Yes, you can file RTI to Delhi Metro Rail Corporation (DMRC). DMRC is a company with equal equity participation from the Government of India and the Government of Delhi, built and operates the Delhi Metro.
Since it is a joint venture between the Government of India and the Government of Delhi, it comes under the ambit of Section 2(h) of the RTI Act 2005 as "Public Authority". Hence, we can file RTI to Delhi Metro Rail Corporation Ltd.
You can file the RTI Application to DMRC either Online or Offline by addressing the same to the designated "Public Information Officer (PIO)" and by paying the prescribed fee.
To know more about the procedure to file RTI Applications Online,please refer https://onlinerti.com/how-to-file-rti-online-for-center