The identified conductor is being used as a phase conductor. The blue tape is to keep someone from thinking that it is the grounded/neutral leg. The equipment inside (not installed) will be rated for 2,000 amp. The POCO sizes their conductors for the expected load. The lineman is probably still seeing spots.
It looks like the black conductor in the back is smaller than the other three. That is probably why they used the striped one as the 3rd leg. It looks like they used their standard single phase UG triplex and threw in another smaller conductor for the grounded conductor.
it pretty much sum up with UG wires our POCO do pretty much the same as well here we used 1/0 AL for 400 amp service but go 600 amp they used paralled 1/0's and majorty of them used bundled triplex and they useally dont stock not too many quadplex unless unuseally large service.
Pas de problme,il marche n'est-ce pas?"(No problem, it works doesn't it?)