Basically systems use an ordinary front loading washing machine and tumble dryer, but they must have controls and or programming to allow for control of water level, temp, wash action, time, etc (washer), and remaining moisture level (dryer). Some special finishing equipment is required as well if one is going to be doing woolens such as trousers, jackets and such.
In a nutshell, items are "laundered" in water containing a high concentration of special detergents that besides being able to clean with minimal agitation, contain chemcials to keep textile fibers from swelling, block dyes from bleeding/runnng, keep any dyes and such suspended in water and prevent them from getting onto other laundry and so forth.
Laundry is washed for a short cycle time (about 5 to 8 mins), then spun, then rinsed for a short time in the same low water level, but instead of a detergent, a softening agent is added which does much of the above, but leaves a protective film that will be activated upon contact with heat.
Items are spun after the rinse, then put into the dryer until a certian moisture content is reached. Yes, even wool and woolens, but not for along period of time and if the proper chemicals are used there is little risk of shrinking. Things are then taken out of the dryer and finished.
Finishing can be anything from blocking dry for sweaters, to using tension presses for trousers and jackets.
All and all wet cleaning seems to work well for things like cashmere and other sweaters,some silk blouses and perhaps a few other things marked "dry clean only", or "hand wash", or "professionally clean"
When Consumer Reports tested various methods of "organic" dry cleaning, including wet cleaning, the later was found to be great for sweaters and some silks, however lined and heavily constructed items like jackets, pants and such had problems such as shrinking, felting, and so forth.
You can find out more about wetcleaning here:
Click on "Back Issues" and then search the archives.
http://www.natclo.com/