It is my pleasure to inform you that as of last Monday, there's a new Expreso Punta Cana starting up. It's the same folks as Expreso Bavaro but with the difference that the station is going to be in Punta Cana and not Bavaro.
For now, there'll be 1 bus daily, leaving Punta Cana at 8am from Plaza Genaro en Veron (soon to be changed to Plaza Galerias in front of the airport). From Santo Domingo the bus will be leaving from the same point at 2:55pm, with pick up in parque Enriquillo and supposedly will go all the way to Nuevo Juanillo which is basically CapCana.
I'll let you know if I get more information.