This topic certainly has generated a lot of controversy.
It would be great if some of the grease manufacturers revealed what the ingredients were in their products so that we could make more informed decisions but that probably will not ever happen.
Without that information all that we really have is anecdotal data with the most impressive data coming from large 2-rail museum layouts.
I agree with Pat in that I have never seen grease attack plastic. My concern about Tacky is that it is so viscous that it may prevent adequate release of heat in a plastic gearbox cases which are sometimes found in 2-rail locomotives. The excess heat could weaken or warp the plastic. This is an educated guess from someone with a degree in chemistry. I may be wrong or I maybe right. Regarding lubricity, the NGLI specs maybe a guide.
