Is there a way to hook up SignalK to networked Garmin plotters?

I'm buying a 722SX to replace my 720S, and the 722SX has LAN ports. It supposedly is able to share sonar data from the transducer, and I would of course love to have that on my forward steering position. I suspect it's totally proprietary, but there's always a small glimmer of hope...or maybe there are other things to read out of the plotter with a network connection to SignalK?