It's always refreshing when the Internet surprises you with an unexpected find.
When surfing for Pocket PC RSS Readers, I came across a reference to FLITE a Text-to-Speech engine based on Festival. FLITE is targeted for the embedded market and as such doesn't offer the breadth of options that one would expect from a desktop TTS library.
It does appear that it is poised to accept voices from the Festival effort. The 8khz voice that is included is limited, but inteligible.
A pre-compiled version for the PPC with a basic GUI can be found here.
The appearance of FLITE may now facilitate moving BlogTalker to my PPC.