Maybe a dumb question, but is it possible to set up multiple brokers with the same account at a clearing firm or some other method to achieve the following? Lets say you have an open position at broker Z and for whatever reason you can't close a position at broker Z (generic routing issue to broker Z, issue with broker Z's system, static from nylon underwear, take your pick) and you therefore decide to execute the closing trade at broker Y. You want the net result to be no position, not 2 open (and opposite) positions. I suppose for equities you could probably arrange a transfer of the long position to the other broker, who may then do some voodoo with the clearing firm to cancel each other out, but that'd probably cost more time and money than it's worth. Probably better to just wait for broker Z to become available again and close both positions simultaneously. Anyway this thread made me think about that as a possible use of a backup broker.
If you have an account over $500,000 and have a DVP relationship set up, you can execute at the other brokers to close your trade, then DVP the stock to the other broker.
You can use the NinjaTrader platform to connect to multiple brokerages concurrently including your Interactive Brokers account. You can try it out for as long as you wish free of charge connected to your IB account. http://ninjatrader.com/ConnectionGuides/Interactive-Brokers-Connection-Guide