The links Sibino posted are:
a page of the site of the State Archives, with an inventory of what is kept at the bishop's see of Treviso. At a first glance, they don't seem to have acts of baptisms before XIX century;
the site of the diocese of Treviso;
if you are looking for a particular parish, it brings you to
http://www.webdiocesi.chiesacattolica.i ... gina=11331
where you can find addresses and phone numbers.