I think it depends on many things, such as whether people at your university are generally collaborative, and whether your advisor or you are well connected. Most of my time is spent on tools or fundamental research, since that's my primary interest; but sometimes people will reach out to me (or vice versa) about starting a collaboration. But even just exchanging notes and chatting with researchers in other disciplines has been fun.

But that is just my experience. Some of my labmates had PhD's in which the majority of their work was collaborative, across disciplines.