The CBI will brief the Joint Parliamentary Committee examining the 2G scam on the progress of its investigation into alleged irregularities in the spectrum allocation on the 28th of this month. The JPC Chairman P C Chacko told this to the reporters in New Delhi on Wednesday. He said that the JPC had asked all agencies probing the 2G scam to brief it about the progress in the investigation into the alleged irregularities in spectrum allocations.The Chairman said the CBI, Enforcement Directorate and Central Board for Direct Taxes (CBDT) are probing various aspects of the alleged irregularities in the 2G spectrum allocation. He said the probe is being monitored by the Supreme Court.