Pete's response is:
A good comment - on the money .
The bottom of this site http://www.fairbanksmorse.com/marine/ indeed points to Fairbanks -Morse diesels being used for backup on Ohio, Seawolf and Los Angeles class nuclear subs. MAN diesels also on the F-M site here.
Virginia class diesels (bottom of another site) were described in 2004 as Caterpillar 3512B V-12 Twin-turbo charged engines.
The characteristics of backup diesels for nuclear subs might be different than for continuous long range use on conventional subs (SSKs). I'd be happier if F-M was still supplying diesels to SSKs rather leaving this market years ago.
Why did F-M leave that market? Was it part of the US avoid building diesel-electric propulsion subs at all costs policy?
I think regular tried and tested submarine Kawasaki, MAN or MTU diesels would be better for Shortfin rather than again specially developing "new orphan" engines like the Garden Island-Hedemoras (GI-H).
Yes Australia's inexperience (and trust in Kockums in the 1980s-90s) was readily apparent. ASC and the RAN no longer had Vickers or the UK RN (Parents of the Oberons) to protect Australia in the Collins project. GI-H's were one submarine class ORPHAN diesels which would have been good for the cold, short distance, Baltic, but remain a constant problem for Australia's warm wide ocean requirements. Tried, tested common-in-submarine-use MANs or MTUs should have been selected for the Collins instead.