@AC
" I would view "X worked for Y from A till B." as the worst possible reference possible."
Some companies are so paranoid they won't say anything bad or good about the ex-employee, in case giving praise could result in legal problems at a later date. The result is the sort of pointless XYAB statement described above. The reason for this is companies do not have souls and couldn't give a monkey's about ex-workers.
All of my ex-employers have either gone bust or rendered themselves untraceable from my CV
through rebranding, takeovers, or simple relocation, so a prospective employer would have a difficult job finding anyone able to supply a reference anyway.