Tobacco Mosaic Virus is actually pretty easy to spread mechanically. Making wounds in the surface of the plant material is required. Insects are not vectors of TMV or other tobamoviruses (yes, that's the term...) It is also not lethal to plants. It will cause some chlorosis and a bit of necrosis and puckering, and then in turn some stunting, but the tomatoes will still flower and produce (in fact the flowers seem really resistant to infection). Steve, if you totally lost all your tomatoes last year,there might be another problem. If you do think it's TMV, it can overwinter in infected debris and reinfect the next crop. It's really a common virus, and I don't think combining tobacco seed and tomato seed is a good idea.Viruses do greater damage to very young plant material, severely altering the metaboloism. In any case, I think it's a good idea to keep smoking out of a garden for many other reasons.
best to all, lisa in Mpls