Yes -- this happened to our 2003 2.8jtd at 98000 miles. I'd just bought the vehicle, and had the whole underside thoroughly pressure washed and waxoiled (RustBusters -- excellent), and noticed afterwards that there was some "surplus black waxoil" dripping for longer than should have been the case (you expect this a bit). Turned out that the sump had rusted sufficiently to have a slightly porous patch about 5mm in diameter, to had to have a new sump fitted at about 110 quid, plus of course new oil, which is about another 75 quid. The sump pan isn't cast, but a relatively complex thin steel pressing.
The realy shocking thing about this is that when you think about it, a sump pan should never have a chance to rust while on the vehicle, as it will dry out with heat whenever the vehicle is driven. Therefore, this is consquence either of the vehicle sitting in a damp field for months before original delivery, or (more likely) the part being slightly rusty before the vehicle was assembled.
Remedy: brush off and Hammerite (or something) the new one. Should help long term.
