The Star ALliance should protect you as best they can. If a member fails at the least Star should reaccom you on another member, and you'd think they would not bother with the extra mileage of going on SQ or NZ because it would be an invol change/reroute.
However I am sure someone at Star Alliance HQ is working on policy even as I type.
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RichardMEL, UA 1K
A Star Alliance Member.