This is talking about just a pure +/- stat. BPM according to BB Reference is "a boxscore estimate of the points per 100 possessions a player contributed above a league average player, translated to an average team". That has very little to do with the actual plus minus of a player when they are on the court. As far as +/- is concerned Rubio was a +250, Baynes +130, Saric -67, Carter -89 and Kaminsky +42.
Ultimately not a great stat to hang your hat on as all of the returning players had a very negative +/- as well. As for BPM Baynes was +0.2, Rubio 0.0, Saric -1.1, Carter -4.0 and Kaminsky -0.9. The key players that didn't return were Crawford -6.0, Okobo -5.9, Jackson -4.8, Daniels -4.4, Bender -3.4, Melton -2.6, Warren -1.7 and Holmes +1.4. Booker (+0.8) and Ayton (+0.2) are the only returning players from last year that had a positive BPM.