Forgot about that other thread. I think i brought up catacholamines as they basically drop insulin to resting levels by 30 minutes into a workout. During a hard aerobic workout it's impossible to spike insulin, I don't know about resistance training, I don't think there's research there. However, the PWO environment is very insulin sensitive, peaking at around 30 min.
I'm going to have to ask someone for the reference for this data because I can't find it. I only know one of the authors. But, what it shows is that if PRO is taken immediately after exercise, insulin will only rise to about 15 micro-units/L. If just CHO is taken, insulin rises to 40-60 micro-units/L, and if PRO+CHO is taken, insulin rises to 60-80 micro-units/L. As far as I know, protein itself isn't insulinogenic, but specific AA's are. Arginine in particular can spike insulin, but to be significant would need to be taken solo in a decently large dose.
Another thing about PWO carbs is that glycogen depletion inhibits protein synthesis. It creates competitive anabolic processes and the body is more apt to replenish carb stores than synthesize protein.
Overall I'm not saying there's any harm to a pre workout CHO+PRO shake, but I think you might as well hedge your bets by taking CHO+PRO after a workout as well. As for fat gain, if the workout is sufficiently difficult (i.e. glycogen depleting. a number of studies show that resistance training sessions can deplete muscle glycogen as much as 40%) then PWO carbs will be pretty well managed. As far as I know there is only one study saying that pre workout protein is superior to post workout protein. However, though I have nothing to support this, it does seem that if you took a sufficiently large does of CHO pre workout and mitigated the CHO depletion, the effectiveness of a PWO protein only shake might be improved. But I think there's some CHO+PRO synergy beyond that.