Hi
Have been thinking about this issue and just though I would type out some ideas and thoughts...
Paper bag smell as mentioned here (
http://www.curry-recipes.co.uk/curry/index.php?topic=8269.msg73813#msg73813) - I have to agree, when we get a TA from the local, the poppadoms come in a brown paper bag and the bag smells great. I agree it is odd to stand there sniffing paper bags, but there you go....
I have a big dedicated bhaji and poppadom frying pot which since its last change of oil has now had around 50 or so combination Rajah and TRS poppadoms cooked in it and no bhajis so far. When the poppadoms are cooked and stood in the toast rack to drain, they smell identical to the aroma from the TA paper bag and the TA's poppadoms.
What does this conclude so far? - not a lot

- however when I cook a curry I generally make several poppadoms too to accompany the curry. The combination of these two goes a long way to satisfying all the aroma senses that one would expect from a BIR style curry. Obviously it cannot be just like the TA because they are making many other dishes too. But the key aroma is there.
This basically leads me to mull over at least the following:
I don't really detect or taste any different oil background in the curry from the BIR's and TA's I have been to in the local area (Fleet, Farnham area) in recent times. But when I open the TA bag it has the aroma we are all talking about, and generally expecially strong when there are some poppadom and or some bhajis in there too. Is that aroma actually in the main curry such as the madras? - tipping it out onto a plate by itself and isolating it from all the other stuff it appears to loose the aroma.
Is there any reasons such as hygiene laws, new or recent or have always been that would prohibit the re-use of fryer oil in another food product that would be subsequently prepared or sold such as a base gravy?. Such that at one time it would have been wide spread practice but now only a few places do so out of habit, cost cutting, or just because that is the way their chef does and has always done things?
What if there was no re-used oil added to the base or the the final dish and in fact there is actually only the aroma of the fryer oil impregnated into all the TA packaging? - after all, the fryers must be on every night all night producing huge amounts of oil vapour into the whole of the kitchen, some of it must seep into every surface, pot and pan.
But we do know however that the occasional TA does use fryer oil such as the one that Haldi has asked and seen doing so.
I would suggest it is worth giving our friends the poppadoms a little more credit for the aroma too. Its not just about the bhaji's stealing the aroma show I suspect!