I'm wondering if this would work with 40 Watts incandescent bulb in series in 120 Volts circuit?
I would be careful here. The lamp is designed to operate from a 28V supply and have 12V drop with a resistive ballast. That is the operating point, where the real power varies only very little even when the arc voltage starts to drift due to any reason (temperature, so mercury pressure; these are saturated vapor lamps after all...), so it will inherently suppress virtually any thermal instabilities. Constant current drive (that the 120V feed via a resistor is) will make the real power proportional to the actual arc voltage, so if the lamp will have higher than normal drop, the power will get higher, heating the bulb further, releasing more mercury, increasing the drop even further. And because there is a filament parallel to the discharge, this will get overheated and fail soon in the process.
Plus not sure, if this lamp will be able to handle first both polarities (so whether the cathode emission mix is really on both electrode end sections of the filament). The description indicates the polarity (negative on cap), so it is likely the filament is formed into the cathode (thicker, coated with emission mix,...) only on one of its ends.
Second the lamp may increase its pressure so arc voltage as it warms up. That may mean the lamp won't be able to reignite after the zero cross anymore, so may start to cycle. Or the reignition voltage would be so high, it would cause the filament still connected in parallel to the arc to overheat and so fail soon. The DC supply it is designed for keeps there the constant 12V and that is what the filament is designed for to handle long time.
I also wondered how would this starting method if this was in the DC circuit as described at that site
Initially it is just an incandescent, where the heat from the filament will warm up the "electrode" sections (the thicker end sections, usually coated with an emission mix as well) of the filament to the thermionic emission. Once electrons get released, the discharge ignites.