Hi Piyush,
Interchangeability is more of an SNP term however, it can still be used along with RBA rules in GATP as RBA rules can either take Supersession Chain ( through Interchangeability group ) or Substitution Procedures ( be it location or product ). To the best of my knowledge, we use Interchangeability attached to RBA rules to allow the same product to work as both active and inactive substitution scenario in different rules whereas if you're using the Substitution procedure ( apart from controlling the validity ), you would not be able to have more control.
Hope this helps.
Babu Kilari