Cant due to unavailability of data...can only make guess.
My guess, its around 150GB per month.
Reason of this guess is as below
1. BSNL is the biggest ISP in India, as per June subscriber numbers they are 8 times Jio or 3 times of Airtel.
2. BSNL alone is like 40% of Wired subscriber in India(BSNL ~80 Lacs vs Total subscribers in India ~200 Lacs)
3. Majority users on BSNL are still
ADSL with daily FUP plans...people here mainly use around 100GB per month
4. Unlimited plans (for reasonable prices) have come up recently. it will take some time for usage to increase
5. For wireless most common plan is 1.5GB per day. translating to 45GB per day that too if the user is using 1.5GB everyday
6. Poll on this forum will be tilted towards higher side of usage, as we on this forum are users with above average data usage.
7. Compare the case of Australia NBN network. They reported average ~250GB per month Dec 2019. They are much higher speed tiers here. Minimum 25Mbps/5Mbps kind of plans with Unlimited data. (And this county stream contents over the Internet a lot, Hardly they have cable
TVs)
Usage in India will increase multifold.
1. Increased availability of FTTH
2. Uptake in OOT Apps. slowly DishTV, Cable TV are gonna die
3. Smart Home/surveillances increase