Misra, who was also the Secretary in the Telecom Ministry, had taken over the chairmanship of TRAI from Pradip Baijal in 2006.
The retired IAS officer, who arrived at the CBI Headquarters in forenoon, was questioned in detail with regard to the policy and other issues relating to the spectrum allocation policy, agency sources said.
Misra had reportedly written to the then telecom secretary in January 2008 objecting the first-cum-first-serve policy adopted by the department in the allocation of 2G spectrum to new operators without specifying its availability, they said.
The CBI has arrested former telecom minister A Raja, his personal secretary R K Chandolia and former telecom secretary Siddharth Behuria in connection with the case. The agency has also arrested a promoter of Etisalat DB telecom company, who was an alleged beneficiary.