Check the NEC handbook. Section 400.7 & 400.8 In their comment {not enforcable as Code} it states: "may not be used as a substitute for fixed wiring ...or where concealed behind... ceilings (including structural, suspended or dropped-type ceilings)."
The Handbook is intended to explain and establish consistency in understanding the Code.
In other words a ceiling is a ceiling even if it has accessable panels. If you wouldn't allow it above a fixed ceiling then don't allow it above a suspended ceiling.
Alan- an Inspector
