The reason filters don't work as normal with this film is because it is a "false color" film.
"False color" means that each layer is not physically dyed the same color as the light that exposed it, like with normal pos. film. With a #12 in place, with this film, on the final transparency, IR light is captured in red, red light is captured in green, green light is captured in blue, and blue light is not captured at all (AKA black).
Normally, a color pos. film has three layers, one sensitive to each of the primary colors of light. This film has three layers as well; the same three layers as normal: after processing, red, green, and blue. They are just sensitized to different colors of light than a normal film. One is sensitive to IR, one to red, and one to green. All three are also sensitive to blue. Thus, without a yellow filter, each layer's density is also being controlled by blue light. Therefore, the baseline "normal" for this film to act as I just described is always with "minus blue" filtration in place.
Which yellow filter you use simply controls the amount of blue light that makes it to the film. With the "baseline" #12, no blue light shows up. If you can't get the #12, I am certain that a #8 or #15 will do the trick. We aren't scientists, so it will be good enough, IMO.
To figure out how to monkey with this film in different light sources, since I hear in this thread that a #12 is no longer made or hard to find, I suggest investing in a #8, a #15, and a set of CC gels and a filter holder. You have to think about the false color characteristics I mentioned above when trying to tweak things with the CC filters. If you want less green, then you need to tweak filtration in a way that decreases green in the final transparency. What color light controls green with this film? Not green light, like with normal films, but red light. So, to decrease green, you need to decrease the amount of red light hitting the film. Thus, add cyan filtration.
Remember, with a #12 in place:
Blue light = black tone
Green light = blue layer
Red light = green layer
IR light = red layer
...and yes, the only place I learned all this is from the data sheet.