I've been listening to Celibidache's EMI recordings of the Bruckner 8 & 9 ((from the mid-1990's) the last couple of days, and was wondering how he would have done with Mahler, particularly the M9, M2, and perhaps the M6 and M10 Adagio. Of course by that time in his career, his interpretations had gotten REALLY SLOW, but I find them very fascinating, and the Bruckners at least have a wonderful glow and intensity that (for me) make up for any lack of speed. I don't believe he did much Mahler (and almost certainly not that late in his career), but I think it would have been interesting to hear. I see that the OP already listed Celi for M1, but I think the ones I mentioned would be better suited to his late-career style.
Russell