If those Celtics games that are showing in the guide as being on 620-1 this upcoming week, are listed correctly (and if they are indeed on 620-1), they are NOT NBA League Pass offerings, but CSN NE-HD offerings.
The NBA blackout rules clearly state this:
Example of How Blackouts Work
The Lakers are playing the Rockets and both teams are broadcasting the game locally — KCAL-9 in the Los Angeles area and FSN SOUTHWEST in the Houston area.
NBA LEAGUE PASS subscribers living in the Los Angeles area will be blacked out within the Lakers' over-the-air territory. To see the game, they must be able to receive KCAL. Subscribers living outside of the KCAL coverage area will receive the game via NBA LEAGUE PASS unless they live in the Houston area.
Subscribers in the Houston area will be blacked out of the game in NBA LEAGUE PASS,
but subscribers can view the game on their over-the-air television station or their local regional sports network (RSN) — included with CHOICE programming and Local Channels.
DIRECTV - NBA LEAGUE PASS Blackout Information
Let's see if 620-1 is lit inside the Boston DMA for the road games this week.