We have mentioned on several occasions that FX Synergy was never designed to work only with MetaTrader. Over the past year we have been preparing the backend of FX Synergy to support other trading platforms, and we recently announced support for NinjaTrader, coming in Q1 2014.
Since we keep getting requests for TradeStation support as well, we have now decided to work on finalizing TradeStation support in Q2, 2014. Right after NinjaTrader and cTrader is supported, which is the most requested platforms.
This means that all features in FX Synergy will be available with TradeStation, and multi-account trading and trade copying will ofcourse be fully supported as well, so you can mix and match accounts on all supported platforms completely transparently.