They have been using them since (at least) the '80's when they were using No1 Mk3's.
Mine are not the best, but they are not too bad. I can think of lots of Enfields I'd rather have but instead of constantly striving for more, sometimes it's good to be satisfied with what one has...
I guess the earlier ones may have been made from locally-produced 2A / 2A1 rifles.
That SLR in the background may also not be a real "SLR", rather by the look of the rear-sight it could be one of the variations of the INSAS (INdian Small Arms System) 5.56 rifle.