Lionelzwl2012, you basically have it correct in your understanding. There are some exceptions though, which I will try and explain.
The original BPC and ASC, etc, have very complicated commands (by button presses) from the cab1, which was all that existed when those products were designed. The Legacy system takes a different approach to control, for example you can get throttle commands on ACC IDs.
As such, the LCS iPad app will not send the correct command sequences to the BPC, ASC, etc. With the Serial interface (SER2) you will still be able to use the older tech with the cabs, but the iPad may not support them directly.
This is why we had to create the ASC2, BPC2, TPC2, AMC2, etc. The newer Legacy commands make for a nicer user experience, and the LCS iPad will leverage this new capability. An exception is the switches (TMCC capable); these use a simplified command sequence and are system wide compatible.
I realize that some folks may be quite unhappy that some of the older ICC controls boxes won't be supported under LCS. The problem goes quite deep, even the ICC controls boxes don't have consistency! Pick an older BPC (pre Lionel) and the BPC of current design, and they operate differently. With time, we may be able to support them by configuration on the LCS iPad app. For now, some limits are going to exist.
