Dallas is off to a horrendous start offensively (23rd in the league in offensive rating), in large part due to the struggles of Lamar Odom. 19 games into the season, LO is shooting 33% from the field, 24% from deep and 59% from the line. And it's not like he's not shooting a lot: he's 7th on the team in minutes, but 4th in FGAs. He's also averaging a career-low 21 mpg, as Dallas is using him more as a traditional back-up 4, instead of the 6th man role he had in LA. The only time he gets to play alongside Dirk, in fact, is as a 3 (which I believe is contributing to his offensive struggles: shooting too many threes/jumpers).
Meanwhile, Boston is using Brandon Bass as a 6th man for the first time in his career. Other than that last chaotic season in Orlando (when half the big man rotation got shipped out for wings and guards and Bass and Anderson flip-flopped as the starter) he's played back-up 4 minutes (averages 19 for his career). This season Boston is playing him near starter minutes (28mpg) and asking more from him offensively than at any other point in his career.
I can't think of a better role swap. The Mavs get back Bass to play the 20 mpg scoring role he thrived in '08 & '09 and the C's get Odom to reprise the 30mpg 6th man role he played in LA.
An additional benefit for the Mavs would be the likely cap savings of the $2.4 mil in Odom's buyout next year with Bass almost guaranteed to opt out of his $4 mil option.