Here is the requirement to be Indigeneous. The third point says ,Not Included in Hindu cast system I guess newars are Hindus.

http://www.nefin.org.np/list/Definition-of-Indigenous/5/0/4

• First settlers  prior to the formation of Gorkha and Nepal state. 
• Dominated group and no representation in state organs 
• Not included in the Hindu cast system.
• Own language, culture and religion different from the rulers.
• Listed by Nepalese Government Indigenous Act 2002.

• Fall under Hindu cast system.
• 86% representation in the civil service.
• Not listed as IP’s by Nepalese Government Indigenous Act 2002.
• Not recognized as IP’s in India  and migrated from India to Nepal.