1. If you have a paper ticket or a printout of your itinerary, at DEL you can enter the terminal to check-in at any of the entrances (1-3). This usually will avoid the lines or get you into a much shorter one.
2. If you have luggage to check-in, at DEL you can get it scanned at any of the x-ray machines for scanning and "sealing". This usually will get you into a much shorter one or avoid the scanning line almost entirely.
If other airlines start doing what BA does to help "premium" customers enter the terminal, then lines will soon become a bigger mess -- worse than already, if one can imagine that -- as it's hard enough to have the carts side-by-side that passing is often not possible or going to creat more of a mess.
The patch-method that BA is attempting is well-intentioned, but there is a bigger -- airport-wide -- issue here. I'm curious if the Airport Authority of India is on-board formally with BA doing some of what is reported here -- at least at DEL.