From what I recall (this was circa 2000-2005) fuel in India was really expensive.. we would regularly fuel up to arrival MLW for a KUL-DEL sector. Worked for Lufthansa at the time and I cant recall doing this for any other sectors.
Another time we did tankering was when we did the KUL-CGK-KUL shuttle .. this was with the same set of crew and the crew would usually fill up at KUL with enough for both ways. On two days of the week we had runway closure scheduled for just after our KUL-FRA departure at around 1am (this was at the old airport with only one runway). Considering that a fully loaded 747-400 will take anywhere from130-140 metric tonnes we are looking at a minimum 45minute refuelling time using both wing points. So what we did is to tell the crews to take additional fuel over the KUL-CGK-KUL sector so they would have more fuel in tanks and thereby reduce the refuelling time in KUL. All of the crews were very helpful as they would reap the benefits when they departed a few days later! BTW this wasnt official but nobody questioned it.. Here it's a question of operational efficiency overiding costs/ecological concerns. If we missed our slot and the runway was closed we would have to cancel the flight and put everybody in hotels etc.
Another aspect of tankering is shortened ground time. I know a lot of narrowbodies tanker fuel simply to cut the ground time down. While you can board pax while fuelling is going on there are a lot of things to consider and its just far easier to fill up more fuel in the first place.
Anilv