Per the 2.5.6/2.6.2 Jira Review Meeting held on 2009-12-08, this issue has been confirmed for the 2.5.6 release.
Seth Theriault November 16, 2009 at 5:24 PM
Possible 2.5.6 candidate
Zhen Qian November 9, 2009 at 12:36 PM
r39695 has been merged into 2-5-x branch in 68707
Zhen Qian January 2, 2008 at 3:05 PM
This appears to be non-issue when the whole site is deleted. However, the problem exists when the provider list is updated through the 'Edit Class Rosters' choice inside Site Info tool.
Steps:
1 Create a site and associate with a provider
2 Delete site
3 Create a new site - old site provider associations are "taken"