wes has it - big breweries open up a hole (or in our case 4) in the bottom of the lauter tun, rakes push spent grain into the hole wherre its carted away... fork lifts and bins in smaller breweries, screw conveyors and pondorfs in big breweries.
Spent grain lives in (quite stinky) silos until its dropped into trucks who take it to feed cows. Cows (according to the truck drivers who cart the stuff for us) ******* love spent grain and come running at a pace when the truck pulls up. They scarf the stuff down and as a result (people in white coats have checked) produce considerably less methane than they do if they eat either grass or whole grain feeds instead of spent grain.... methane which they primarily burp, not fart.
On the 200L scale - i'd think about making the lauter tun tip so that it can be raked out easily into a bin. A bit of applied leverage, or some pully action, or even a bit of simple hydraulics could make it a physically trivial job to tip, and raking would be simple and easy. Whereas shoveling/scooping from the bottom of the tun, over the edge and into a bin = ergonomic OH&S nightmare. Save someone somewhere a serious back injury and think of a better solution. Just because micro breweries often do make people get into the MT and shovel it out..... doesn't mean that that particular way of doing it is anything but completely shit in every way, shape and form.
TB