I tend to agree with Jacob Spire. If "can this actually happen?" is the intended question, then it is probably limited by a lack of context -because as we know truth is often stranger than fiction. It would be hard for anyone but the author to answer questions like that out of context from the rest of a specific story.
"Would readers believe this?" is a more accessible question and I would say more thought provoking, however, the answers to this kind of question might not get to what the author is looking for. There are innumerable reasons why a set of circumstances might not be believable to someone. My reasons for disbelief might be completely irrelevant to your story or your train of thought.
As I stated I tend to agree with the previous commenter, but the reason I chose to add my two cents is that I believe there is a great deal to be gained by asking the more specific question:
how could I make this concept plausible, or how could I make a reader believe this?
This gets to the art of fiction. Sometimes I am limited in my knowledge of a specific topic, or the amount of time I have to research. For those situations, I feel like a site like this can be a perfect forum for writing tips that might overlap a bit with physics, or technology, or psychology, etc...
I am not surprised when a seemingly smart character does the smart thing or when a seemingly dumb character does the dumb thing. I am not even surprised when a writer, who might be hurried or lazy, makes them do the opposite with no preface or explanation. What makes for great fiction, however, is when characters really surprise you, to such an extent that you need to stop and ask how that happened. As you look back at the pieces it all makes sense and you just have a little smirk at how clever it was. I know great authors generally prefer to be invisible, but I've experienced this many times despite that fact.
In the end, you are the writer and it is your world. You make the decisions about what is realistic -you and maybe your editor. We can't honestly tell you objectively whether something is realistic in a vacuum, but I do think that talking about technique around specific circumstances is specifically what Writers.SE is all about. Of course, I'm still pretty new to the site, so I could be totally wrong...
Thanks for the interesting question.