When installing a card in a server, the Corporation can first trash any cards already installed in that server.
When installing ice, the Corporation can first trash any ice protecting that server in order to reduce the install cost.
The first quote seems to imply that when the corp is installing any card in a server (including Agenda, Asset or Upgrade), it can trash any card installed on the same server first, including ice.
The second quote is more restrictive, but doesn't seem to actually contradict the first one.
At the same time, I have seen comments indicating that the corp can't trash ice when installing other card types.
So, can the corp actually trash ice when installing other types of cards?