Another vote for 'no'
Although there are times when either emergency or planned closure of bits of the underground (or the central bit of Thameslink) means that underground tickets are being accepted on buses - but this will be specifically announced via TfL or GTR website.
It's also a bit of a pain in the tail late at night / early on Sunday mornings before the underground starts.
At the risk of stating the obvious, options (if you want to do this other than when an emergency hits the underground) are
a) get a travelcard instead - these are valid on all TfL bus services anywhere within London (and on the TfL routes that venture outside the boundary, to the end of the route.)
b) get a 'london terminals' ticket and pay separately for the bus journey - you can not pay cash fares on TfL buses any more, so you will need either a contactless payment card, or an oyster card with some credit on.