In my opinion they use some third party blur transitions. But if u wanna know about what blur effects in VEGAS pro can be used to make this type of video then those will be Gaussian Blur, Linear Blur and radial blur in some places. I don't sure about defocus fx.
VEGAS 19 also has a new motion blur effect. You might also be able to edit a bunch of scenes together in rapid succession like that and use the VEGAS deflicker effect at max strength to achieve a similar look, along with the motion blur.