There are a lot of people who travel from BTM Layout to Shivajinagar for work/pleasure. The only bus that does this route is 161D. There is also 201/164 but those take too much of time. When I began travelling by BMTC, I too used to wait for 161D. But that was inconvenient since the service was pretty infrequent.
Now 5 years hence, I am much smarter. The easiest way to get a bus to Shivajinagar/MGRoad area is from the bus stop opposite Shoppers Stop on Bannerghatta Road. It is a short walk from BTM Water Tank which is close to where I stay. From here you have the G4 that goes all the way to Brigade Road. This is a very frequently serviced route. You can expect a bus every 15 minutes. Same for the return journey too.
If you fancy a VOLVO, that too is available. There are numerous 36x buses that travel from Bannerghatta towards Majestic. All you need is get down at Double Road stop. From there there are numerous routes connecting to Shivajinagar.
This is my daily route and I find it very convenient. And of course the walk obviates any further need of exercise. I hope more people start adopting this route instead of waiting for buses at BTM Layout. It is a greener and healthier option. ( Btw you can obviate the walk too by taking a bus from any of the BTM stops to Jayadeva circle.)