@ Two to Tango
In the April 5 and April 7 statements (press briefings) by the pertinent Malaysian authority - in which the organization and scope of the investigation were outlined, including the designations of three committees as well as other nations as Accredited Representatives - no reference was made to the requirement of an interim report at the 30-day mark, nor to any plans regarding such report. Link to press briefings:
MH370 Flight Incident | Malaysia Airlines
Most likely, the ICAO authorities will have determined that, procedurally, the 30-day clock has been deferred or suspended, given the known facts of the incident - and given also the many unknowns. Moreover, the statements make reference, in a general way admittedly, to the one-month marker. A good and sensible ruling here would be that, by announcing the detailed structure of the investigation effort at the one-month juncture, Malaysia has substantially complied, on the facts (again, some known, many more unknown). E.g., both press briefings do make reference to ICAO standards relative to other aspects of the organization of the investigation, thus suggesting that ICAO tacitly endorses Malaysia's approach.
If anything official has been issued relative to the 30-day interim report, I plead missing it.