This discussion didn't seem to take off, so I'll give it some attention.
I can talk from one perspective: working with a pop singer/songwriter/pianist. (Maybe others can comment on just singers or just solo pianists.) Anyway, she's played solo (piano and singing) most of her life but has only been performing solo in front of audiences regularly for about a year and a half. We've been doing the full band thing for about 6 months.
Two issues come to mind (she visits here every once in a while so I have to phrase this well.

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First, I think when singer-songwriters play their whole lives solo, they're going to develop their own sense of time, both as writers and as performers. As writers, they will incorporate dramatic pauses to fit the mood of the song. As performers, they will always rely on themselves to drive the music's tempo. Getting together with other musicians can sometimes be difficult at first in getting down that sense of "band" time (and understanding the need to no longer command the time and let the drummer be the engine of that band time). I think this comes through with practice and there's really no need to mention it (IMO) unless it's something that doesn't correct itself.
But the drummer also has to have some give here (reminds me of the "immovable time" thread). There are areas in piano-based music written as a solo artist where there are fluctuations in time that help make the song what it is. As drummers, we can't be so tied to metronomic time and need to adapt to the writer's intentions. I think it's vitally important in piano-based popular music for a drummer to have an awareness of when it's necessary to be fluid.
Second, there's the occasional problem of busy-ness. Solo artists have to fill everything up themselves with melody, harmony, counter-melody, rhythm and dynamics. Then, once in a band context, there is a danger if that "solo" focus is retained. Once in a band situation, the artists should pay special attention to not drive everything. They need to be aware that the guitarist can sometimes handle that additional melodic line, or provide the big chord that helps establish the dynamic element the songwriter is looking for. Similarly the bassist can take on much of what's happening with the left hand on the piano. And everyone needs to lay back when there's a particular drum fill during a transition.
I think this second aspect might be the most tricky. The first item can come through naturally with practice. The second element often needs to involve a conversation when collaborating. Musicians need to tactfully speak up when things are becoming busy, and the songwriter needs to trust others help achieve the desired effect. That way the song takes prominence rather than the execution of it, and the music has the space it needs.