Go into quick race and the set the map to Canyon 1, set the type of race to Combat Race and the difficulty to Exhibition and then start the race. You can race around normally, stay with the pack or speed off. When you go over the weapon pad and you get the cable and if you are near to enemies that are close together forward fire (RB) so one end hitches on to one enemy and then press it again to stick it to another enemy nearby and then it should unlock.
This could take some time because you might not get the cable weapon in the race or you might not be able to find 2 enemies close to each other. But you should be able to get it eventually.