It relies on the label whether or not an album gets a digital release, and (unfortunately) most of the time, soundtracks aren't lossless when they
do get a digital release (let alone 24-bit). Nintendo is known for lacking in the soundtracks publishing department, oftentimes releasing incomplete promo albums and only focusing on their most popular IPs (
do they even know about digital releases besides iTunes?).
Brave Wave is a label that releases lossless digital, and
Ninja Gaiden The Definitive Soundtrack did get a 24-bit 48kHz release in
mono.
If you'd like to find more, you can go into
Advance Search, check off 'Digital Release' and go from there.