Overlapping geometries share some portion of their interiors, but one can't completely cover another. This relationship is tested with the ST_Overlaps function. This query will reveal all bus routes that share some part with the E-3 route:
SELECT ogc_fid, other_tags, wkb_geometry FROM multilinestrings WHERE ST_Overlaps(
wkb_geometry,
(SELECT wkb_geometry FROM multilinestrings WHERE other_tags LIKE '%E-3%')
);
Please note that, if a route exactly duplicates the path, or is a subsection that is completely within the bigger route, it will not be included in the result:
A bus route network: the E-3 route (red), overlapping routes (violet), and other routes (gray)