Those are some fantastic images! Proof that growing tomatoes can be an art in more ways than one.
Some tomatoes are hybrids. Hybrids take the fruit characteristics of one plant and combine it with the high-yield characteristics of another. Then when grown in a greenhouse where conditions are absolutely controlled, images like those can be presented.
This man, http://www.youtube.com/user/mhpgardener/videos has produced some impressive videos of tomatoes and seems to enjoy showing everyone how to do it. Scrolling through his list of videos will show tomatoes almost as nice as the ones you posted. He also responds to all comments to his videos, should you have a question for him.
How to get MORE tomatoes (not bigger tomatoes) from a single tree:
Cultivar selection will affect the number of tomatoes more than anything. Some varieties yield many fruits (the cherry tomatoes can produce 100s per plant per season, but the fruit are small) and other varieties produce large fruit, but few of them.
Tomato Cultivar Trial and Pruning Observation
You will get more yield (total season fruit weight) if you don't prune. You might get bigger fruit (but less of them) if you do prune. By pruning, you're effectively thinning the fruit.
The most striking difference at harvest was larger
fruit size (.69 lb vs. .55 lb) from pruned plots. However, pruning also reduced the number of fruit harvested
by 32% and total marketable weight by 15%.
Its possible to get bigger fruit by pruning, but its not guaranteed. I've read studies saying there was no significant difference between fruit size of pruned and unpruned plants. Though there is always a significant difference in total yield.
Removing side shoots may reduce overall tomato harvest. In fact, in a study by Purdue University, and published in Organic Gardening Magazine, scientists found that removing side shoots was shown to increase the average fruit weight some of the time but did not increase the total harvest for each individual plant.
So with selection of the proper variety, having good conditions for growth of tomatoes, and not pruning too much, you can have large yields from a single tomato tree.