I had my BCG whilst in hospital after diagnosis, and had my first hypo shortly afterwards. Could be related to the BCG, but not surprising really as this was after 2 weeks on insulin, when my body was probably becoming more sensitive to insulin, and I'd got more active while I spent a few hours at home each day prior to discharge.
And, you give a newly diagnosed type 2 virtually no carbs, and they lose weight and their blood sugar comes down - surprise surprise!