What do you mean by authentic? There are several Belgian breweries that use T-58. Most of the small ones don't have money for a lab, so their two options are get yeast from a bigger brewery (which many have stopped allowing), or use dry yeast. It might just take some playing with the pitching rate, pitching temperature, oxygen levels, nutrient levels, fermentation temperature etc... to get it to preform the way you want it to.
A few weeks ago I was up in Boston and got to talk to the brewers at Pretty Things and Mayflower, I got to try a beer from each that was made with T-58, and both were very tasty.