Here is some information straight from the HawksStore.com regarding mesh numbers. The guy there is great and even emailed the head of NBA Retail to get clarification on mesh numbers.
"The clarification that I received is authentic jerseys made by Adidas are mesh if the order meets a certain minimum which can range from many hundreds to thousands. We typically don’t order those quantities so that is why we have twill numbers. Many vendors – including us – also buy blank stock then send off to personalization companies to sew on player name and numbers, this allows more flexibility with inventory. This means we can order 1000 blanks and make 100 of 10 different guys vs. having 1000 of one player. The personalization companies do not offer mesh numbers. That is why many vendors could have a mixture or confusion."
So this is why teams like Boston, Miami, and LA have mesh numbers. They sell more jerseys than anyone else and are able to hit the min qtys. I would think maybe the Bulls would be able to do this too, but they still have twill numbers.