In the latest Q&A batch Blizzard revealed that indeed Protoss buildings can be infested and produce units.
Q&A Batch 35
1. Do Banelings damage nearby friendly units when they explode onto an enemy target? (www.starcraft2.com.au)
No, in the current build the Banelings do not damage friendly units caught in the splash. The splash damage does cover its area of effect range evenly, doing the same damage to enemy units throughout the whole area.
2. When a Nydus Worm is detected, is it possible to shoot it down while it is traveling? (www.starcraftcz.com)
Yes, having detectors in strategic places will keep you from being surprised by an unexpected Nydus Worm showing up in your base.
3. Does the Nydus Worm, a ground unit, move through open space? (battle.net) pop.helo
Yes. We dont know how we are going to make this look yet. When we come up with a visual solution we are happy with we will show it to the community.
4. Can Zerg buildings be infested, and if so, what units are produced? (starcraft2forum.org)
Zerg buildings cannot be infested. It is planned that infested Protoss buildings will produce an infested Protoss unit that will play differently than the infested Marine.
5. Will be there such doodads like customizable light or shader? (battle.net) Dagguh
Yes.
6. The first screenshot listed in Karune's 33rd Q&A shows what looks like the Mothership's Black Hole ability. However, it was said that the Black Hole was removed. Does this mean the ability has returned in the current build? (Starcraft.org)
As mentioned before, the state of many of these units are always changing. In the current build, the Mothership has become more of a support unit with increased hit points and decreased speed. The Mothership now allows Protoss Gateways that have converted to Warp Gates to be able to warp units straight to the Mothership. The warp-in mechanic (which cannot be queued) has also been tweaked to allow Protoss players who use it to get a slight time decrease in unit production as opposed to queuing units traditionally at the Gateways. In other words, the cooldown timer on warp-in doesnt take as long as the build time for units at a Gateway.
Furthermore, the Mothership will also have the ability to transfer energy down to casters below it, such as Templars. Both the Time Bomb and Black Hole abilities have been removed.
7. Will Phase Cannons be able to rematerialize on an allys Pylon Power, or an enemys Pylon Power for that matter? (sclegacy.com)
Phase Cannons are no longer able to move in the current build.
8. Is the Tauren Marine going to be included in the StarCraft II map editor? (battle.net) scorpionbrood
Yes.
A Very Good Batch
This batch has been more revealing than previous ones. We have learned about infested Protoss, the new abilities of the Mothership, and there will be a Tauren Marine in the editor! All great news from Blizzard who has clearly been working very hard to create the best game possible.
*Update: The time bomb stays
Despite claiming that the Mothership's Time Bomb ability was to be removed in this Q&A batch it now seems as if those plans have changed. In a forum post on the Battle.net forums, Community Manager Karune states that
the Mothership has the Time Bomb ability in addition to its previously mentioned 'support' abilities.
Regarding the gigantic Protoss vessel's other ability, the Black Hole, it will only be available in single player mode due to balance issues. This has, at this time, been done to try out a more support-oriented role for the Mothership. It is yet to be seen if things remain this way as the StarCraft II development team ensues further experimentation.
Links
Battle.net - Source
SC2League.com - Source