Polycom spiked nearly 13 percent, and Mitel popped nearly 20 percent on Friday. Private equity firm Siris Capital overshadowed Mitel's $1.96 billion offer with a roughly $2 billion, or $12.50 per share, cash bid.
"We are very excited for the opportunity to partner with Polycom and its leadership team, as the Company fits well with Siris' investment focus on mission-critical telecommunications businesses," said Dan Moloney, executive partner at Siris, in a statement Friday.
Siris added that it wants to use Polycom's audio and video collaboration to move into a cloud-based environment.
"While I am disappointed that this particular transaction will not move forward, I am confident in Mitel's future as an industry leader and as a market consolidator," said Rich McBee, president and CEO of Mitel in a Friday statement. He indicated that the company would not adjust the prior agreement.
Jonathan Kees, an analyst at Summit Redstone, told CNBC that Mitel shares were up so much because of three reasons.
"First, they're getting $60 million in break-up fees," he said. "Second, they don't need to issue additional equity to fund the deal."
Lastly, "They're getting more respect from investors because they didn't overpay," Kees said. "Mitel could've counter offered, but they didn't."
Polycom will pay a $60 million termination fee, the New York-based firm said.
Mitel's U.S.-listed shares traded at $7.21 a share, while Polycom traded near $12.25 per share. Mitel and Polycom shares have dropped more than 12 and 2 percent this year, respectively.