On November 10th both companies announced the start of a mutual due diligence process over Vocus' approach to acquire the remaining shares in Amcom which it did not already own.
It followed Vocus' move to increase its shareholding to 10 per cent.
Today's trading halt indicates the month of due diligence may have reached a conclusion. A further announcement is expected before the end of the week.
Market analysts believed the two companies' assets were of mutual benefit with Amcom holding significant infrastructure on the west cost and Vocus the same on the east.
A merger of the two companies would create a company with market capitalisation of $1.2 billion based on current share values.
Early in November Telecommunications giant TPG Telecom also followed Vocus' suit by increasing its shareholding to 6.7 per cent - indicating its interest in a deal, but it is yet to make a formal offer.
Amcom chair Anthony Grist told Business News in November negotiations with Vocus would likely reach a conclusion before the end of the year. He also said that would likely be the time that other interested parties made counter-offers.