In May 2006, ~173MB download during NU hours got charged to my non-NU 1GB/mo. quota
This is the reason why I always schedule to reboot my router at 12:30 from the day I booked this plan last year. Though I never got billed for NU downloads. I do face some connectivity problems as reported by other MTNL users on other broadband forums but truly MTNL rox in my area. I'm wish they start with DU plans soon as BSNL have done in Pune (Rs. 900 p.m)and other cities.
Regards.