Here's a short update on decoding the OpenSky 2 format. This is the narrow 9600 bps (4800 baud) version. The waveform is essentially the same as P25 C4FM. 

http://pspc.harris.com/Solution/OpenSky2.aspx

Folding the data 560, 280, and 140 symbol intervals shows high repetition of data. During idle times it is hard to distinguish invariant data (like sync bits) from idle frame data.

The data is broken up into frames of 280 symbols. Each symbol is two bits. Each frame starts with a 24 symbol frame synchronization pattern followed by 256 symbols of data (64 bytes). The two frame synchronization patterns alternate one after the other. For the patterns below, each digit represents a symbol where 1 indicates a positive arc, 0 indicates a negative arc. If you prefer using +3/+1/-1/-3 with four level symbols then 1=+3 and 0=-3.

011010110001111101011111
011010110101010101111111

Each frame often appears to repeat itself. The first 128 symbols will be equal to or very similar to the second 128 symbols. It is unclear whether each frame is a time slot or each frame carries two time slots. 

Good luck.