Possibly off-topic. There is some literature from the mid 1950s in the area of phosphate esters in which alkali metal halide salts were used for monodealkylation (primarily of benzyl esters IIRC). Some of the work came out of Alexander Todd's laboratory. Unfortunately, I don't have any links, but I might still have a few of the papers in hard copy, in case anyone is interested. I think that the attack was on carbon in this instance. This might be a start if anyone is interested: Lecocq, J., and A.R.Todd, J. Chem. Soc., 2381 (1954).