Hello,
I have a question about this sentence from the linked event briefing:

Pilots may be told to remain clear of the Boston Class B airspace and are not guaranteed to receive a clearance through the Norwood or Hanscom Class D airspace. This means that aircraft may have to alter their route to avoid the airspace or descend early to avoid it.

I have done a number of PRP flights from BVARTCC, and I'm confused about the clearance situation -- in PRP VFR#4, I learned that ATC clearance is not required for C and D airspace, only "contact" with them.  Is it true then from the event briefing that you could be "denied clearance" through Norwood/Hanscom class D?