It was delayed last week when the only remaining board member and chairperson, Mbulaheni Maguvhe, launched court action to interdict the investigation, which was unsuccessful.
He cited alleged bias from opposition members.
Parliament established an ad hoc committee to look into the board's affairs and Maguvhe’s fitness to hold office.
The first group of witnesses to be interviewed today includes Public Protector Busisiwe Mkhwebane and the Independent Communications Authority of South Africa (Icasa).
Parliament's ad hoc committee will sit for 11 days as it looks into Maguvhe's fitness to hold office following a rash of resignations of board members.
