Thanks for your reply!
The key word in that sentence is "report's main dataset includes this in the WHERE clause" . . . in the interest of brevity, I didn't include the whole query, which was quite lengthy.
And, actually, since you brought this up, a later version of the report shipped off the query to a stored procedure, and there, instead of being in the WHERE clause, the filtering on BusinessSegmentName took place in the JOIN - @GLSegment contains the various segments that the user is able to view:
from dbo.uv_TRM_Scorecard_Data SD
-- Added line for INNER JOIN to GL_OU table
INNER JOIN GL_OU AS ou ON SD.GL_OU = ou.GL_OU AND ou.BusinessSegmentName IN (Select Data from Split(@GLSegment,','))
-- Added line ^
LEFT OUTER JOIN dbo.uv_TRM_Scorecard_Milestone SM ON SD.UHT_ID=SM.UHT_ID
LEFT OUTER JOIN dbo.uv_TRM_EST_CostSummary_current SC ON SC.ProjectNumber=SD.UHT_ID