i have never seen yacon syrup here but regularly eat yacon potatoes. they look like a sweet potato but are watery inside, like a cucumber or a jicama. they are super duper sweet and crunchy. they are sold as a food for diabetics because their sugars are inabsorbable (? is that a word) to humans. they are sweet and lovely and one of my favorites fresh.
that said, i live in the land of sugar cane, agave plants, palm flowers and yacon potatoes, and i don't see how any of these syrups can be produced without heating and processing. i often use yacon in smoothies or in recipes that need to be sweet, and there is some interesting research about its use against diabetes, but once it's processed i don't think i'd be interested in it anymore.
there are some interesting links on the wikipedia page http://en.wikipedia.org/wiki/Yac%C3%B3n