That, I don't know. I don't see why they wouldn't have the full 14MHz there, but AJ would almost certainly know better than I. The FCC docs that I found only provide the calls signs for the SMR licenses that Nextel purchased in PR and everywhere else. What you posit sounds quite plausible imho regarding the concern over international interference.
What I like to check periodically is the 800 TA. The latest report came out a couple of weeks ago: http://www.800ta.org/content/reporting/QPR_09.30.12.pdf Pages 29-31 and devoted solely to Puerto Rico and the USVI. If I'm interpreting the document correctly, the USVI is all cleared and ready to go for 800MHz whenever Sprint is ready (provided that there are no interference concerns with neighboring countries) and PR's clearing and re-banding is progressing quite rapidly as well.