I'm certain they won't do una corda since they have to re-record the entire pianos and it would effectively double the size of the download. Frankly I don't even like it on my Baldwin 5'8" grand because when the dampers come down they make a little bit of a twang because not all the strings are vibrating equally. It was that way when it was new. But the sustain resonances would be very simple for them to do.
I've been doing the sustain resonances myself using the sampler Kontakt. If anyone else wants to know how, let me know. It's a bit of work.