Here is some preliminary research:
Peugeot specifically allows 30% blend. Article on green-car-guide.com claims that all Peugeot HDi engines (since 1998) can use UK B30 blend without modifications. That also means same for other customers using PSA (Peugeot Citroën S.A.) diesels (Ford and Volvo in Europe).
VW UK issued a statement (PDF) in March 2010, saying that no VW vehicles approved for use with FAME (Fatty Acid Ethyl Ester) B30 (models with DPF allowed up to 7% biodiesel), and few models allowed with some limitations (nothing below -10°C, for instance) to run on 100% RME (Rapeseed Methyl Ester). Those allowed were often build compatible, but couple required retrofitting kit.
VW says 100% RME fuel cannot be used on common-rail injection systems, but I have read people had success with variety of commercial and home-brew Bosch CR injection on vehicles like 2004–6 (pre-DPF) Mercedes 320 CDI I6 engines (same injection system used on many diesel vehicles), although Mercedes specifically warns not to put anything over B5.
Back to DPF-equipped vehicles with urea dispensers. Officially, it seems that at least Germans do not support B30 without modifications, but from hearsay I do not see definite proof, at least for PSA motors with manufacturer’s blessing, that those people who do have problems with B30 is not an exception (Perhaps, they have used poor quality fuel?).
I did not see many complaints about actual shearing engine wear, just issues with DPF contamination, and problems with seals in components of high-pressure fuel systems (rail, pump, filter etc.).
Commercial fleets seem to jump on biodiesel quite eagerly, even where DPFs are mandated. 20% common in US, 30% in Europe and many manufacturers of big rigs (Mercedes, MAN, DAF, Scania etc.) qualify many or some engines for 100% as well. But I do not know what modifications those engines undergo to accept higher biodiesel blends.