Which operator ‘owns’ the station in question doesn’t seem to make any difference regarding those stations displayed with lockers on the SBB lockers overview page.
Because lockers are listed there also e.g. at St. Moritz (RhB), Andermatt (MGB), Gstaad (MOB), Grindelwald (JB), Engelberg (ZB), Appenzell (AB) + many others. The necessary communication with SBB could however affect the reliabilty of information updates, though.
