While I guess that might ultimately be feasible for a small company could charge their payroll to a credit card, as a prior post notes it would not be economically viable. I.e., the interchange fee charged would undoubtedly be higher than the value of the miles. This assumes that it could even be accomplished, which is debatable.
As for the miles being earned on business long distance charges, yes this can be done. I was CFO for a small company with a long distance bill of $5k-$8k per month. We earned miles via a program with AT&T and these miles were utilized to offset flight costs which we would otherwise have incurred. Hence, no one directly received the benefit.
As a follow-up to the above, as soon as our long distance contract with AT&T expired (not my call initially), I signed up with a vastly cheaper and arguably better carrier. We had a huge reduction in our LD bills and no more miles.
I do not see an economically viable way to accomplish either of the above. I.e., charging payroll to a card may not be possible, and even if it were it would be too expensive due to the interchange fee. You can receive miles via a business line, but your LD costs will be high.
One thought for you which I almost employed at my prior gig. We had three corporate credit cards which the CEO/CFO/COO used for dinners out, etc. By chance, the restaurants that we frequented were largely within the Dining Miles programs. I signed up my card and earned a number of miles. I came really close to signing up the cards for the other exec officers (I had the #'s, of course), but did not think that this would have been an ethical action. Hence, I passed. -Might be an idea for others, you never know.