virnaem:
FWIW, the IB TWS (both 3.0 and 4.0) use the FIX 4.1 protocol (with some proprietary fields added) via an Internet gateway.
I would be interested in hearing of the results of your conversation with IB sales. I suspect they may try to sell you FIX over a frame relay connection, which may be a little much for the average individual trader. If this is in fact the case, you have a supporter here who has some ideas on access that may be acceptable, both to IB and its technically inclined individual customers.