The Lutron Radio RA2, RA2 Select and HomeWorks systems all use the Lutron Connect bridge. Phyiscally this appears pretty much identical to the Lutron Caseta bridge although also seems to be black in colour vs the white Caseta model.
It would appear that despite being effectively identical hardware and speaking the same wireless proprietary protocol it is using sufficiently different software. I would have thought however the differences would likely be small enough to make developing a version to link from Smartthings should not be too hard.
Frankly I regard RA2 Select to be a complete and utter waste of time. Their in-line modules do not support linking to wired switches and hence if you still have wired switches have the same problem as you would with smart bulbs. Also as has been pointed out UK regulations require having wired switches.
If only Lutron would wake up and do a European version of Caseta - even if it involved micro modules which could like Fibaro be wired to a physical switch.