Not for the purpose of GHG accounting. The reality is that a PPA is simply a financial contract that can take a variety of forms (e.g., a price hedge), and so a PPA is a malleable financial arrangement that is not intended or designed for attributional GHG accounting.
Given that RECs and other voluntary types of contractual arrangements or instruments (such as PPAs) are typically used to make GHG emission reporting claims, this question reduces to being about whether PPAs are a proper basis for assigning indirect emissions for GHG accounting. Although evidence is currently lacking as to the impact PPAs have on renewable energy investment and generation, it is unambiguous that the wide range of different contracting and financing provisions that fall under the “PPA” label in different legal and power market contexts is not a sound instrument for attributional GHG accounting (see questions Does buying a REC or GO mean I am using renewable energy?, What are the “environmental benefits” or “attributes” associated with RECs and GOs?, and What does it mean for an electricity generator to “deliver” electricity”?).