There are lots of examples of this already, just off the top of my head:
Donald Fagen - The Nightfly - recorded on 3M's 16 bit/50kHz multitrack system and mixed to 16/44 digital, the 5.1 DVD-A is a sonic improvement on an already great recording
Donald Fagen - Kamakiriad - recorded and mixed entirely 16/44, the DVD-A is a better and warmer mix
Roxy Music - Avalon - the 5.1 SACD is mixed from 16/44 PCM backups of the original analog multitracks, and it's considered one of the best-sounding mixes of the SACD/DVD-A era
A while back when I was trying to figure out what Richard Chycki was doing with his Rush 5.1 mixes, I was comparing the 5.1 remix and original stereo mix of Signals, from 1982, which I guess was mixed to 16/44.1 digital because even the hirez stereo remasters have a hard dropoff at 22kHz. Even though Chycki is an absolute hack as a surround mixer, there was no denying that the 5.1 mix had an extra level of clarity, mostly because it was free from the "digital glare" that the original stereo mix had, presumably thanks to being mixed from new transfers of the analog multitracks and mixed to a higher resolution format.
The one thing that people who think that CD resolution is "enough" and that hirez digital is a waste seem to not want to acknowledge is that A/D and D/A conversion technology has improved markedly and audibly since the first digital audio recording and playback devices first appeared in the early '80s. Obviously there are a million hurdles in getting a new remix right (or wrong) but all else being equal, from a purely sonic standpoint I think most recordings finished to early digital technology could be improved, even if the new remix was at the same CD-quality resolution.