I know only two types of MV ballasts that are used in the US and Canada: HX, which is similar to series choke and don't use the capacitor as the ballasting component, and CWA, which requires the capacitor and provides constant current and voltage to the lamp.
Well, there is a CWI - but it is the same as CWA, it only has completely isolated secondary from the primary. But except mass and losses (both are significantly higher than of the autotransformer type), it works exactly the same as CWA. It is required in Canada when the lantern supply is the 240V across phases - to have the lamp shells grounded (Code puts an alternative in a socket that ensures no connectuion to the shell when it is possible to touch by a finger, but haven't seen any ever existed except European E27 and E14 incandescent sockets).
Technically a HX isolated would be possible as well, but I don't know if that ever existed (places needing 240V are usually the remote ones, where the supply voltage fluctuates as well, so the HX won't work there).
