Found more specific information on Berg Lake Trail, overnight and day use:
http://bcparks.ca/explore/parkpgs/mt...perating-dates

Of interest, trail opens 6-15 for registered overnight backpackers. Still closed are Picnic Shelter at trailhead, Hargreaves Shelter (at Berg Lake).
This suggests the other, open-sided shelters along the route will be open.

Trail opens 6-15 to day users, who must register; registration will be conducted on back deck of the closed Visitor Centre.