It has been a busy week for the TV Everywhere test project.  First, two premium movie networks — HBO and Starz agreed to participate in the trial, and now CBS, the first broadcast television network, today announced it was signing on as well.

CBS will be running a mix of older and current shows as part of the trial with Comcast subscribers, probably including its popular shows like CSI and NCIS, which are already available in some areas online through Comcast’s “Fancast” portal and through Time Warner Cable’s Primetime on Demand channel, available on digital cable.

“CBS and Comcast share the same vision of giving consumers more — more content, in more places,” said Matt Bond, Executive Vice President of Content Acquisition, Comcast Cable.  “On Demand Online is a major step in extending consumers’ television experiences online, and ultimately across platforms by giving any television network, including top brands like CBS, the ability to make their content available on the Web.”

CBS historically has avoided partnerships with the cable industry.  It is the only network that never launched a cable network (ABC Family, MSNBC, CNBC, fX, and others on offer from other networks), and also steered clear of a partnership with Hulu, which has ABC, Fox, and NBC among its partners.

The network is interested in the potential exposure its shows might have on-demand, particularly among younger viewers.  But more importantly, being friendly to the largest cable companies around may prove fruitful when the network wants retransmission consent agreements signed, permitting cable companies to place the network’s owned and operated local TV affiliates on the cable dial without a lot of aggravation and negotiations over fees.

TV Everywhere will offer “authenticated” subscribers to cable television or satellite service access to on-demand, streamed video programming through broadband networks.