Theoretically, a 4.5 means the same thing at Tiers A, B and C. Listening and reading are capped in Tiers A (4.0) and B (5.0), however. As a result students may not fully demonstrate the proficiency that they have obtained in the capped domains. Students deemed likely to score a composite PL of 4.0 should be given Tier B or C. For more information.
A student can be eligible for exit if they score a 4.5 at any tier, but multiple measures must be taken into account before exiting. This link has some sample forms that you could use to capture the multiple criteria that you use when exiting students:http://www.nj.gov/education/bilingual/resources/indicators.htm
For more information on required multiple criteria please see 6A:15-1.10(c) of the New Jersey Bilingual Education Administration Code: