Remastering is a pretty broad term. Some remasters are actually remixes using the multitracks or stems from them. But in any case, it's down to the taste and equipment used by the mastering engineer. Even back in the analogue days there were quite substantial difference in sound between LPs depending on where they were mastered and cut. It was not uncommon for US and European records to be cut from different generations of mastertape. As well as generational issues other factor in remasterings is the fact that the mastertapes (assuming that the original master and not a copy of it is actually available). Tape deterioriation can apply to early digital recordings as well as analogue since the latter were tape based - DASH and VCR based systems like the PCM F1. However, for recordings that were originally mastered to digital from one inch 30ips Studer/Otari etc. analogue machines, there is the potential for remastering on modern ADC's to make a very substantial improvement in SQ.
