So i have been pondering purchasing Out of the Abyss for the maps. But my question, and one i couldn't seem to find the answer to online, is does it ever work that way? Could i, for instance, buy the module and download the maps for use? Example : one of my groups i run is an online group, and we have been testing tabletop simulator for online play for 5e. Would I be able to download the maps from the module and upload them into tabletop simulator for use?

Definitely. The module comes with every map in high-res, a simple click and you can download them.