In my own experiences, they have kept their stuff and then took the household furniture along too. In some, they just kept what was in their family inventory and nothing else. So my answer would be yes. I did however, move a family from one town to another and they also kept their belongings, but the price of all of their gems and skull pieces went way down in price, which rather upset me. I had skull soulpeaces that were in the hundreds of thousands of dollars and after the move, they were like 5,000, but that was from one town to another. I think your sims inventory should be fine.
Edit: I see now your actual question, was about evicting. I can't be 100% sure, but I would think, to go to edit town and evict would still keep their inventory in tact. I don't know though, if you put them in the library and then move them back, if they keep their stuff. I am trying to remember if I have done that. I would hate to tell you one thing and not be sure and you lose the belongings. Geeze, I can't remember what I did yesterday, lol.
