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You should be just fine with G+ authorship as long as in the clients' pages you have the rel=author links in there. Yes, there are alternate ways of establishing G+ authorship, but it's my understanding that the explicit 2-way links are the core means of identifying the author-document relationship, and that the alternate methods are just that. I think it's pretty safe to verify these using Google's own structured data test tool.  Yes, it has a few bugs, and fails to read some websites, but it's overall pretty reliable, and I would expect that it's using a very similar bit of logic to determine authorship that the SERPs-producing code is using.

That makes sense. So basically the answer is that Google is smart enough to tell that it is your actual business name, and not a website you bought to rank with.  Thanks!