So I had to test this out, and it works very nicely. Referring to the cheap chinese scaler that Sabroso linked above, I chained after the OSSC in the capture side of the output. It handles the transitions well. 480i pass thru looks the best out of all the 480i options (shown below) – no noticeable flicker, nice smooth edges. It is scaling from 240p line3x to 1080p very nicely as well. A little bit of clarity loss and maybe colors aren’t quite as perfect, but pretty darn good for what it is, imho.
480i OSSC output modes supported: passthru, 2x, 4x
240p OSSC output modes supported: passthru, 2x, 3x, 4x
This is captured by elgato camlink: