The spiritual activity described in Powers and Principalities is based on actual biblical doctrine, although some liberties are obviously taken to fill out details such as the appearance of the demons, and what they say to humans and to each other.
The primary Scriptures that serve as the basis for the story include:
Revelation 12:7 (war in Heaven)
Mark 5:1-20 (demonic possession of humans)
Ephesians 6:10-18 (the nature of spiritual warfare)
1 Corinthians 10:19-21 (demonic involvement in people's worldly indulgences)