You'll find some decent, if basic, info on the RBST website on them. I know a few people semi-locally keep them and I'm quite likely to be going for Scots Dumpies myself whenever I get around to building a run et al. They're also kept at Palacerigg Country Park (Cumbernauld) and at Culross Palace, which has been very useful for me to be able to observe them for a while.
The info on eggs I've picked up on so far is that they're decent layers, but not as frequent as modern hybrids and their eggs, while medium, have a lovely creamy flavour.