It looks like there are parallel light trails below each streelamp -- going down, then right, then down some more (ASCII art):

 /
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  \
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And highlighted on the original: I would guess that these are when the shutter button was pressed, tilting the camera, because only bright sources show this effect. This is in addition to the normal, more horizontal/wandering light trails. If you view full-res you can see the individual pulses of light caused by the AC power (fluorescent and similar lights used to run at twice mains frequency, but newer models like these are high frequency). These pulses are more widely spaced in the long straight of the trail, close together (they run into each other) where the camera is changing direction more slowly. I can tell these are high-frequency lights because counting the pulses at the usual 100-120Hz twice mains frequency would account for a significant proportion of your exposure time, and the windows on the opposite buildings demonstrate that this isn't the case.

Zoomed in on the pulses:

This also shows the tail light trails you'd expect, indicating that the disturbance didn't last for very much of the exposure.

The solution is to reshoot ideally with a tripod and a cable release. You can improvise for the tripod but then the cable release becomes essential (or wireless release, or self timer, just don't touch the camera). Even slamming doors can make the camera move. I'd turn off the IS - it can't help you on such long exposures, with the possible exception of vibrations through the floor.