When, under normal circumstances, may a Technician class licensee be the control operator of a station operating in an Amateur Extra Class band segment?

An amateur radio operator may never exceed the frequency privileges granted by their own license class. As a Technician class licensee, you are always strictly bound by Technician class limits whenever you are acting as the control operator. Even if you are using a station owned by an Amateur Extra class licensee, or transmitting from a club station whose trustee holds an Extra license, you cannot legally operate in an Extra-only band segment. If an Extra class operator wants to use those frequencies on that radio, they must take over as the designated control operator.