The opening for a Frontier topping bid

Verizon's agreement to buy Frontier Communications appears to have an open line for other parties to join the call.

Why it matters: The lack of any shareholder voting agreement in early filings around this particular merger opens the door for a counter-bidder to step in.

Zoom in: Verizon announced its $9.6 billion agreement to buy Frontier yesterday, offering $38.50 per share. Including debt, the deal is worth $20 billion.

• The stock traded just above $35 per share on Friday morning.

The intrigue: Frontier was bankrupt four years ago, and three distressed debt investors still own nearly 40% of its shares.

• Ares Capital Management owns around 16% of the stock, while Cerberus Capital Management and Glendon Capital Management each own close to 10% of the shares, according to FactSet.
• When a company has that high a concentration of private equity/distressed debt investors still in the stock, it's not uncommon for the buyer to try and ensure their support with a so-called shareholder voting agreement — in other words, sign here so we know you're good with the offer, can lock in your backing and can wrap this all up quickly.

Yes, but: A review of Verizon and Frontier filings so far shows no such agreement in place.

• That means either Verizon was super-confident that Frontier shareholders were supportive of the deal or Verizon tried and the investors declined.

• Ares, Cerberus and Glendon are keenly aware that there are other companies interested in Frontier's fiber.

What we're watching: AT&T is one company that has built a massive fiber network, is large enough to be an acquirer and would presumably want to give a company like Frontier at least a look now that it's in play.

The bottom line: It's early days, and the deal has just printed. But with no Frontier shareholders locked into approving the Verizon deal, the gate is open for an interloper.

All companies mentioned in the story did not immediately return a call for comment.