I'm an avid symphony patron, and I also watch different symphony orchestra recordings online. I've noticed that sometimes an orchestra will be in white tie, sometimes in black tie and other times simply in a business formal style with matching ties. I've noticed this in person with the same symphony orchestra and recorded performances of other world symphony orchestras.
For the concerts I've attended in person, I can't identify anything special about the occasion to warrant the more formal dress (white tie or black tie).
This leads me to wonder if it's related to the piece they are playing.