PBA players aren't handled by the government in terms of vaccination. Not the usual, 1st priority will be healthcare, then seniors, then so on.
The government allows private companies to purchase their own vaccine with a certain condition currently that there should be donated to the government (if I'm not mistaken 50%). The agreement to the vaccine manufacturers will be done by the private companies themselves. And since there are lots of countries and companies from other countries too in-line, at any manufacturers, like I said, it might take months before the league can settle a vaccine.
Once the league was able to secure its own supply of vaccines, it can proceed anytime with its own vaccination program outside of the government's priority list.