I would tend to agree with you:

Those MR lights look like Carbon Arc lamps... the predecessors to HMIs for ca. 20k of daylight. I was still ACing in NYC 14 years ago I last saw them used. That film was shot in 1998. 3 years later I moved to Europe and never saw one over there, just on big budget Hollywood films. They required one man per light, unheard of today; but, the method yields the smallest light source after the sun and the cleanest, consistent daylight color temp, better than HMIs (so a Gaffer told me).

If memory serves: the light is generated by pumping DC current down a rod of carbon, until it arcs to a rod of copper. The carbon burns faster than the cooper and rotates and feeds forward to burn the rod evenly. After ca. 5-10 minutes the light starts to flicker and needs to be trimmed using the knobs on the back and a built in sight glass which looks like welders glass. All that burning generates smoke which comes out the top and sometimes requires ducting to keep if from blowing into the shot! The sides of the lamp open up to change the rods when they become too short and eventually to service the feeding mechanism. Another old timer Gaffer told me he once had an electrician that would bring a raw chicken wrapped in tin foil to work and stick it inside his arc lamp. When they called lunch, he was all set with his slow roasted chicken!

Often it was the Gaffer who wanted to use carbon arcs to cut down on the PITA discrepancy in color temp between aging HMI bulbs when shooting celluloid (before digital intermediate was available)... pure "analog" as a European friend called film.

From my NYC dayz... Gaffers: Gene Engels, Dick Quinlan and Tim Guinness were all fans of arc lamps; as were the DPs they lit for Caleb Deschanel, David Watkin and Rob Hahn (Gene said he had to convince Rob to use arcs...)

Here is a theater in New Jersey advertising carbon arc projection! Wow! http://8mmforum.film-tech.com/cgi-bin/ubb/ultimatebb.cgi?ubb=print_topic;f=8;t=001797

Old but good technology, and it needed a lot of man power! Makes me appreciate my GH2 even more.