GE Form 400 just after firing up, along with series incandescent acorns

Located in Santa Ana, CA. I just caught this series loop lighting up as I was taking pictures! There are two GE Form 400s at this intersection, on the old Union Metal fluted steel poles. The other Form 400 was out when I took this pic, I was told it had a HPS lamp, presumely a HPS retrofit lamp. The one in the picture has a metal halide lamp. The ballasts are most likely series mercury ballasts, original to the fixtures and poles. The shaded OV-20 that was converted to incandescent is located just one block behind this spot. I notice the remaining incandescent acorns appear to be pretty dim for a 2500 lumen light source, maybe perhaps they still use the 1000 lumen lamps which have been out of production for a while. Several are brighter, prolly 2500 or 4000 lumen lamps. Many also got low wattage metal halide lamps with plug in ballast adapters. I have a feeling these lights will eventually be converted to LED. Maybe the series circuits will be retained, with the LEDs operating on the STM transformers such as the ones now made by Jim Terry and his company OV-20 Systems.