Correct - I thought it odd that the OP listed WNJB as the nearest ch. 58, but a Wikipedia article is only as good as its author's research. WDPX would have been my first though, but the discription of programming was not Ion's programming.
In any case, Boston is far enough from Vineyard Haven that a co-channel LPTV station was allowed there. Analog WCEA-LP had a severe null to the SE to protect WDPX. Digital WCEA-LD is on a different RF channel, so Vineyard Haven is no longer a problem, to them. Their signal now must avoid interference to full power stations in Hartford CT and Portland ME.