It's impractical, but that hasn't stopped a lot of people from doing it and enjoying it, as you can see if you scroll through the talkloid posts you see floating around. You can make a singing vocal synth talk, but it's a pain because you have to manually create the timing, spacing, pitching, expressive settings, and pausing in musical notation for what in a TTS program would be as simple as typing text and adjusting how the words are emoted. The difference between talking loids (Voiceroid, TTS Programs) and singing loids (Vocaloid, Utau, Piapro, etc) is how the UI and program handles them.
IA English has no talk library for CeVIO, it's the Japanese IA Talk library.