(For the record, I was ninja'd by TINT for the first half of this)

Looks to me like the operative phrase here is that Telepathic Insight says "Faction-specific effects."

"While your squad contains only Fringe characters" is not an effect, it is simply a requirement. Similar to how GOWK's CE is rangeless but applies to characters with an ally within 6 squares - the 6-squares bit is not itself a "range" for CE purposes but a descriptor of who the (rangeless) CE applies to.

Talon's +4/+10 is technically a boardwide everybody-gets-the-gimmick CE just like Rieekan handing out Evade and Mobile to absolutely everyone in the squad, it just so happens to not activate unless your squad only has fringe characters.

EDIT:

Another thing to note is that boosts that require Fringe-only squads definitely play more like descriptor-based boosts (i.e. "Pilots get +X" or "Order 66 gains [insert ability]) than other Faction-focused CEs. Like, there's no good reason to play a Pilots-only squad for the heck of it; you're simply cutting yourself off from the Rebels other resources. Likewise, Fringe characters can already be in any squad, so there's no inherent reason to restrict yourself to them. Show me a good Fringe squad and I'll show you a better Imperial squad with those same Fringe characters but adding Thrawn.

So Talon's CE is effectively more of a reward for restricting yourself to a certain descriptor rather than a generic faction boost. From the perspective of what Talon is meant to do for your squadbuilding, it wouldn't be any more in the spirit of the law for the Vong to take Talon's +4/+10 than it would for them to be able to cash in on an enemy Lando's Specialization.