Well, I'm pretty well convinced that the designer intended target size mods to apply to ATT shots:
11.2 EMPLACEMENT: The To Hit procedure vs a Gun which has not been hooked up and which has not been moved since the start of the scenario (11.3) can be resolved in either of two ways at the firer’s option. An Emplaced Gun can be fired on using the Area Target Type (the Gun’s Target Size [2.271] is a To Hit DRM unless inside a pillbox/cave; B30.32 and G11.83) with a +2 TEM (once hit) for being Emplaced; or it can be fired on using the Infantry Target Type, with the +2 Emplacement TEM and the Gun’s Target Size used as a combined To Hit DRM. For OBA or other FP attacks, the +2 Emplacement TEM applies on the IFT [EXC: FT; A22.2]. In all cases, however, the Emplacement TEM cannot be used in addition to any other positive TEM; the Gun’s owner may choose one or the other, but not both. There can possibly be different To Hit Numbers for units in the same hex. A Gun can never be Emplaced on a paved road, bridge, runway, Rooftop, or in Bamboo and does not receive the +2 TEM while manned by a squad.
Now... did the designer intend target size to apply to Smoke, which he (presumably) knowingly used the ATT to define how it is fired?
I think so, and the reason I think so is because of the +2 TH modifier when firing Smoke within 12 hexes. The rules offer us no explanation for this modifier.
IMHO that mod is there to offset the effects of target size, concealment, etc. So far as I have read nobody who feels the size mods shouldn't apply has addressed the +2 modifier. For me that is an overall significant increase in the effectiveness of firing Smoke, which I don't have any reason to believe (from a reality or a playability point of view) is necessary.
Personally, I don't think a ruling is necessary, and agree with Chas... if Perry sez "no size mods for Smoke shots" it will be a rules change.
However, I also think that there is NO question about the RB that is a BAD question. Any information that we can get from Perry that makes it so that we can ALL play by the same rules is valuable information.
Happy Presidents Day!
JT