Yes, You can file RTI to Indian Railway Catering and Tourism Corporation [IRCTC] , Indian Railway Catering and Tourism Corporation (IRCTC) is a subsidiary of the Indian Railways that handles the catering, tourism and online ticketing operations of the Indian railways and it has been set up by the Ministry of Railways. Since, the Ministry of Railways is a ministry in the Government of India therefore, IRCTC shall also be treated as central Government.
It is a public Authority and It comes under the ambit of section 2(h) of the RTI Act'2005.
To have a brief understanding of the procedure to file RTI to IRCTC you may visit the following link:
https://onlinerti.com/how-to-file-rti-online-for-center