One pair of leaking calipers on one bike out of a production batch in a no no ,but it can occur .
Numerous sets (some fitted to the same bikes ) and from production runs possibly a year apart and therefore from different batches of supplied calipers by the same manufacturers (Hayes ) are an absolute f*cking disgrace.
BMW have promised owners that it was a bad batch but it has been rectified which it obviously has not , Just in Time Manufacturing will mean that neither BMW nor Hayes will have months worth of calipers sitting in stock.
I don't give a flying f*ck that BMW have an excellent warranty system , this is a safety related issue as no vehicle on the road should have a brake fluid seepage , leakage issue or whatever you want to call it . A ten year old vehicle would fail it's MOT for a brake fluid leak , never mind a vehicle just off the production line .
I didn't change my 1200 for a 1250 this year because of this and other known issues and having been a BMW Beta tester in the past I would not care to go through that sh*t again.
Personally if I was picking up a new bike and it had from new or as in many cases quickly developed a brake fluid leak from defective calipers I would reject it on safety reasons , good leverage for them swapping to Brembo calipers or supplying you with a replacement vehicle from a new production batch fitted with them at the factory