I would not be surprised if some campaign managers have enrolled (with ease) their own purchased accounts, farmed accounts or alt-accounts in order to maximise their income (effectively cheating their employers).
Though the probability of this happening is possible, but I doubt a campaign manager who manages lots of campaigns will engage in such dubious act of creating multiple alts, and accepting them in his signature campaign as an avenue to maximize profit, most especially when he manages lots of signature campaigns to manage and also has the duty to examine and count posts of it's numerous campaign participants. Because I think this can only be possible when a manager has fewer campaigns to manage like 2 or 3.
If you were to take a guess, which percentage of accounts enrolled in a campaign are actually owned by the campaign manager? I will not mention names of the highly respected campaign managers that I am certain do not cheat via this nefarious activity because the attention would fall on the managers I did not name (when attention should fall on them without me mentioning names anyway).
Asking us to guess what percentage of accounts been enrolled by campaign managers on their respective signature campaigns will be a mere speculation, until proven otherwise. Because I'm pretty sure not all campaign managers has an alt in all it's signature campaigns. Because if they do, it wouldn't be in all, but one in a few selected campaigns, since owning an alt account is not a crime, but joining it in the same campaign is it.