There is one significant point of comparison between the two series - only one - and the entirety of "Paramount stole this" originally hung on that premise: they are both set on space stations. This was a departure for Star Trek; Berman and Piller reasoned their way to it in a fashion similar to the way that jms supposedly did.
That only sounds suspicious if you've never been through the process of reading spec scripts, for example, or slush pile manuscripts for an sf magazine. There's a fairly good - if brutal - short essay by John August here
that addresses an instance of how ideas parallel one another when working within the same envelope and toward a similar target.
B5 was going to be a show that solved a lot of the budget and logistics problems of doing future-based "space opera" stuff like Star Trek
, and key to the solution (at least as far as pitching it was concerned) was that the expense of building an elaborate "home base" would be amortized by making that the primary location - the action comes to us rather than us going to the action.
Berman and Piller had exactly the same problem to solve based on their years of experience actually doing
a Star Trek
show. If you buy the notion that using a space station was a flash of unreproducable brilliance as opposed to what it actually is - a fairly easily deduced solution to production cost problems - then you might more easily swallow the notion that coincidence is less likely than unnecessary and illogical theft of a simple idea.
But the truth of this situation doesn't hang on what you're willing to believe. Some things actually happened, and other things didn't.