The sentence in your "Nachrichten in leichter Sprache" is correct in terms of grammar.
Indeed a sentence like
Es gibt vier neue Parlamentspräsidenten. Es sind die Herren Müller, Maier, Schmidt und Schulze.
is correct since the numerus depends on the count of things (or here: people) refered to.
Or using a different example:
"Da steht was Dunkles in der Ecke." - "Es ist ein Weihnachtsbaum."
is correct since it is one (!) Weihnachtsbaum.
"Da steht was Dunkles in der Ecke." - "Es sind zwei Weihnachtsbäume."
is correct because there are two.
(Please be aware that so called "Leichte Sprache" is a newly invented form of German that is oversimplified to the extent of being actually wrong even in terms of basic grammar (not to mention style here). For example the evangelists of "Leichte Sprache" insist on not using genitive forms, claiming that the clientele they intend to produce these texts for is not able to understand genitive. I find this concept questionable. That's a different topic, of course. But don't start to speak to normal people like that. You would be in danger of being looked upon puzzled.)