Does Spotlight search work with a Time Capsule? I would like to use a Time Capsule as a file server for 3-4 Macs in a small network. 
I've 600 GB of data, and a lot of small files. My colleagues work a lot with Spotlight to find files. I would like to ask you: does Spotlight search work if I use a Time Capsule as a file server?
Yes.
Per default, it will be indexed. You can opt-out any location in...

System Preferences → Spotlight → Privacy

If you add and remove a location in the privacy tab, it will be re-indexed.
Also see Apple's support document Spotlight: How to re-index folders or volumes.