Not sure if I can quote a Codex word for word, so I won't, but...
Smart Missile Systems have 'Homing' which yes allows them to be fired at units outside of line of sight.
It's a Tau specific rule, I think, not sure if any other races have 'Homing' but there may be a few out there? IG/AM Basilisk can shoot without LOS, but suffers full scatter is closest I can think of.
Not sure of a pg ref, taken from digital version.
See above, beat me the draw lol