Can one slice of a "Disk Utility" RAID mirror be moved to a new computer? With a 2-disk RAID mirror created in Disk Utility, after one disk fails, can the remaining good disk be moved to a different Mac and used successfully?
Theoretically, yes.

But remember Apple's RAID solution is software based so both computers should have the same O/S versions. 

But if you are moving a boot volume AND the hardware is the same it should be cake.

Moving a boot volume to DIFFERENT hardware... well I've never tried that. It might work and it SHOULDN'T damage the drive data. 

YMMV