Conceivably is an adverb, and has no tense.

Not typically, but they conceivably could.

possibly, conceivably, perhaps, might be, can be

Not necessarily. The Narrator could conceivably hold this position.

Your question is not clear. Conceivably you want the definition of the word plan, conceivably you are concerned about some specific plan which you have not identified, and maybe you mean to ask, what is the plain answer to the civil question, although you have not told us what the civil question is, either.