"The level of fear and uncertainty is a huge issue," Roehrig said, "and a competitive differentiator is how the vendor manages that change."

To clarify the situation, the two parties need to talk early and often. Customers should expect open communication, visibility into strategy and financials, clear deliverables and a project plan to manage change, he said.

A common fear is that service levels won't continue to be satisfactory. But for the most part, Roehrig said, it's in the acquirer's best interest to maintain them in order to avoid breach of the contract. "The goal is to keep the customer and expand the delivery footprint," he said.

Scheuble agrees. When an acquisition occurs, "everybody's at risk," he said, "so it's important to get on the same page and identify the big issues early on. There's always a way to modify the contract so that everyone gets something they want."

The discussions should continue as the transition unfolds. At Trex, a big issue was getting a clear view of the new provider's policies and procedures, which were more formal than the previous ASPs. "They have a much more tightly defined and well-documented way of doing problem resolution and taking requests," Richards said. "There was a period of uncertainty where we had to get used to that."