There is no way to get OSC-messages in ReaScript.
However, by using the reaper.OscLocalMessageToHost-function, you can send a local (means Reaper-internally-only) OSC-message with an optional 14-bit-value-parameter, which can be read by the function reaper.get_action_context.
Maybe you can find a way to trigger that behavior from OSC to at least be able to send a value that is seen by reaper.get_action_context()...
Apart from that, I haven't seen anything yet.
Edit:
I made a FR for that
https://forum.cockos.com/showthread....78#post2353178