Well, here’s what a note in the C++11 standard, [dcl.init.list] p1 says:
List-initialization can be used
- as the initializer in a variable definition ([dcl.init])
- as the initializer in a new expression ([expr.new])
- in a return statement ([stmt.return])
- as a function argument ([expr.call])
- as a subscript ([expr.sub])
- as an argument to a constructor invocation ([dcl.init], [expr.type.conv])
- as an initializer for a non-static data member ([class.mem])
- in a mem-initializer ([class.base.init])
- on the right-hand side of an assignment ([expr.ass])
Since this doesn’t mention the conditional operator, your compiler is right. Also note that the conditional operator expects expressions on the both sides of : ([expr.cond]), and a braced-init-list is not an expression.