The requirement to publish data in the IATI standard by 2012/13 forms part of the Memorandum of Understanding between DfID and the organisations (para 19).
According to the accompanying letter:
"Each PPA partner is required to submit an annual report to DFID for appraisal. The format of this report has still to be finalised but it is intended that it will include a requirement for all PPA partners to show the progress they are making towards becoming IATI compliant."
DfID should publish these annual reports automatically (but if they don't I expect they'll be obtainable under FOI).
About 40 of the largest development NGOs receive funds from DfID through the PPA. Once each NGO has set up the mechanisms for publishing DfID-funded projects in IATI format, there won't be any excuse for not publishing information about all their other projects too.