I did one (QS/TE + 14001) that was not really a sale, but one company splitting into two. The management system was never really set up for the entity being split off, so we built a new one that fit better. The original registrar would not cut any deals on a registration audit (would not even waive the application fee), so we had another registrar quote it and awarded them the job. The plan was for a one day document review and "assumption" audit from the old registrar to the new. Due to internal politics, the main company chose to pull ahead their surveillance audit a month, which left too much time between that audit and our readiness for the assumption, so we had to go through a new audit and the spin-off technically lost their registration for a short time (no customers noticed).
Basically - Company A spins off Company B, which is still in the same building. Company A sabotages B's cheaper option for an assumption audit. Registrar A gives outrageous quote, so Registrar B handles new Company B registration. Two companies with same (basic) name, in same building, with two registrars. Very strange situation.