I read the original thread in posted in 2005, but in my personal experience this is not an issue here in the DR. I married my wife in the DR in 2000 and a protestant(pentecostal) pastor presided over the ceremony. We also had the town official, Dr. Guzman, from Moca there as a witness.
BTW, I'm Catholic, but other than that the Catholic Church had no say whatsoever over the marriage ceremony.
Also, in the event you are interested in having an Episcopal pastor preside over the wedding, there are quite a few here on the island. Here are a few examples with a link to the yellow pages following:
Iglesia Episcopal Dominicana
12 No 18 A Rosa, Santo Domingo
(809) 596-5196
Iglesia Episcopal Dominicana
Santiago 114, Santo Domingo
(809) 687-9259
Iglesia Episcopal Cristo Redentor
Las Amapolas 2, Puerto Plata
(809) 586-3327
Iglesia Episcopal Cristo Redentor
Sánchez, Puerto Plata
(809) 586-6575
http://www.paginasamarillas.com.do/Default.aspx