I would think it was handled as you suggest, out of PDS on an ongoing "time and materials" basis. Main reason? Why would TPL absorb this cost on their own when there is risk involved, and when they wouldn't be the sole beneficiary of the effort? The ONLY reason would be so they would hold the trump card if things, for any reason, went awry. But this reason holds no water - they already held the trump card.
JMHO,
SGE