Multisite

I don’t think so, sorry.
You could try it, but I guess it won’t work properly. Brutal Cache was designed to improve single user blogs at free hosting services, because of the shared amount of resources on this systems wordpress might be very slow and heavy. But with Brutal Cache this blog can be hosted at an freehost like square7 or funpic with much more speed.

Sorry, I’ll hope you’ll find another solution.

No problem. I opted for Quickcache. Seems to work well enough. It would be nice to use your cache even on a multisite install on paid hosting though. A blog like mine which is a shopping portal could really benefit from it. https://adshopez.com/