score:10
It appears that information is in fact not listed in full on public websites.
So I called them and asked about specifics at the Brig train station:
Prices and available sizes do vary between locations (source (german)).
In Brig, there's two sizes of lockers (width x height x depth):
Source: SBB Rail Service (+41 900 300 300 (premium rate number, CHF 1.19 / min))
Baggage Office
Mon–Fri 07:00 – 18:30
Sat 07:00 – 18:00
Sun 08:00 – 12:00
13:30 – 18:00
Lost & Found
Mon–Fri 07:00 – 19:00
Sat 07:00 – 18:00
Sun 08:00 – 12:00
13:30 – 18:00
Source: SBB service opening hours (Brig)
Note: These opening times only refer to the offices (baggage / lost & found), access times for your locker are usually longer.
I couldn't get exact details for access times to lockers in the Brig station, but this page for lockers in Zürich main station lists them as
Sat–Sun 24h
Mon-Fri 00.30–04.30 closed
so I assume the situation in Brig is at least similar.