Ben Orr was not much for effects live except for chorus, and he did that line on several different basses throught the Cars' live days, and it always sounds the same. The night I saw the Cars in 79, he did it on a Precision, I believe. On this night in 84, he definitely used a Precision:
http://www.youtube.com/watch?v=_p6a7CiP2bM
On the studio version, it's being doubled by something doing an octave down and a keyboard synth. Can't tell what the octave down is. But live I don't hear the octave down, and on that clip I posted, I can't even hear a synth doubling it. You could use an envelope filter and an octave box to recreate the studio sound to a certain degree. But on the live clips I don't hear any effects on the bass at all. Just whatever bass through a mic'ed SVT. That's what it sounds like to me.