if this person is the MiVB admin, yes, they can set up silent monitoring for any phone.
but no, there's no way to monitor a phone that isn't in a call.
Mind you, the admin could set your phone up to auto-answer and call in and it's just be a speakerphone at that point.. The display would should you in a call but if no-one heard the answer tone or noticed the display, well...
You need to have trust in your admins, they have a lot of power.