Megasteam is the equivalent or rather better. TAS smoke fluid was thicker and harder to clean up from engine surfaces But produced a decent amount of smoke.
I think that 3rd Rail's owner's manuals say that their engines are equipped with temperature regulated TAS smoke units. The last one I looked at did seem very much like the old TAS models but they have been out of production for years. I've found the performance of 3rd Rail smoke units uneven. My latest models really have needed the wicking re-packed and saturated before use.