At what point in the typical Product Development Lifecycle is QA supposed to create a Quality Plan? I would think prior to creating a Test Plan. But how much earlier in the lifecycle does QA have enough information to create a Quality Plan?
It does depend on what your company defines as a "Quality Plan".
I consider a Quality Plan to be a "what"/"how"/"when" document, with the "What" being a statement of the quality objectives, "How" being the activities that the project must undertake to meet those quality objectives and "When" being when in the project lifecycle the activities are going to be performed (which will probably not be absolute dates, but phases in the lifecycle).
As such, the Quality Plan should be written as soon as possible after the project has been defined (requirements defined and project team assembled).
Is that it, then? No, it isn't. There are a number of factors you can't know at the beginning of the project and the Quality Plan needs to be revisited near to the end of each cycle or major milestone to prepare it for the next piece of work. I all too often see it as a once written, never referred to document, rather than as a tool to use as part of the project - and it can be very powerful to maintain and use the document throughout the life of the project.
Somewhat controversially amongst some of my QA colleagues, I don't advocate QA being responsible for the Quality Plan, I believe it is the Project Manager who is responsible for it and s/he may delegate the writing of it to QA people.