Can't read beyond the paywall but this has been in the news in a few places. Sounds a bit like von Neumann's 'astrochicken' idea, as elaborated by Freeman Dyson:
Although I dunno if the Milner/Hawking idea is anything advanced as self-replicating automata, as von Neumann originally envisaged:
It says the project's advisors include Avi Loeb, Saul Perlmutter, Martin Rees, Dyson and Sagan's widow. That's a pretty A-list line-up!