Can people with multiple personalities interact with their alters?
If you have shared consciousness, then yes.
With my gf, she has shared consciousness between the alters. She can feel when another is around and there is arguments in her head a lot.
She has a ‘mind space’ which is a room where all of her alters have beds. They are all decorated and she has no control over it at all, it just appeared and apparently is quite common in people with DID. They all sit and talk, comfort each other and argue within the mind space. Often she spends large amounts of time in there, especially if someone is upset and she doesn't know why.
She also only has a Birdseye view of it.