In 1991 though it was pretty useless for an album production, only offering 4 tracks. Looks like the shift started to happen around 1997.
"The first version of Pro Tools was launched in 1991, offering 4 tracks and selling for $6000USD. Digidesign continued to improve Pro Tools, adding a sequencer and more tracks, with the system offering 16 bit, 44.1 kHz audio recording. In 1997 Pro Tools reached 24 bit, 48 track versions. It was at this point that the migration from more conventional studio technology to the Pro Tools platform took place within the industry."