I merged a total of 4 numbers onto my account almost exactly 1 year ago and made a "mobile share" plan. To my recollection, those that had unlimited data kept it until I formed the mobile share group, even those I transferred in. That was 1 year ago though, so policies may have changed.
To the OP's question, the other guy should be able to transfer responsibility out and keep the number and the unlimited data. As for you, I would keep your unlimited data and number out of the company and just let them do what is best for them.
To the OP's question, the other guy should be able to transfer responsibility out and keep the number and the unlimited data. As for you, I would keep your unlimited data and number out of the company and just let them do what is best for them.