James,

Since the title belongs to an administrative and financial position, there is no liturgical warrant for such a person to be alongside the Pope at any Mass. The one in the job, as a clergy member, may happen to be among those attending/con-celebrating Mass with the Pope, but it would merely be coincidental.

I did a Google image search and didn't find any images of the Pope with the Camerlengo appearing alongside, at the office or at funerals, so I imagine it is not commonplace at all.

I hope that helps.

Peace,

Bob Kirby