I would check into that. I know you can use REDI to hit marketmakers and other ECN's, you get charged the REDI fee plus additional fees for ECN's and SOES charges. This was the same with ARCA, they have smart keys, but you still end up paying that charge.
Unless you have some type of different arangement w/commissions with a flat structure, your paying the charge. No way ATTN/LSPD would give REDI a special deal just cause its an ECN, more reason to charge them full price, why give an ECN part of the liquidity that you have to have?