Answer to original question...it depends. I would say that one high intensity session per week will result in adaptation. However, training is very much athlete specific.
The other aspect is duration. Duration is generally more important than absolute power. It is better to do 3x10' of 30/30 than 1x10' 30/30. It is better to ride a 10 minute interval at 95% FTP than an 8 minute at 105% FPT. Duration trumps power.
If you want to do BTS's 3'x3' then commit and do the entire workout. That will generate more change than let's say doing a very hard 3' effort and then say, I am gassed and cannot do any more and quit. That has been my experience.