I have doubts that McCabe would divulge anything of value anyway, with or without immunity. Unless he has already lied to the FBI and knows he's about to be charged for it.
His boss, James Comey tried to throw him under the bus. partially resulting in the IG recommending his indictment.
Were I McCabe, I would be more than a little pi$$ed and possibly out to even the score. McCabe has already publicly declared Comey 'misled' and should not be believed. The fireworks in court should be, potentially, something to see.