What would have been helpful here would have been to "resolve" the ambiguity earlier. First question to resolve would be is or isn't the road signs to be part of the technology scope. You say the Contractor "considers" them part of that scope but is that correct or not. If it is part of that scope the ambiguity should have been raised earlier and resolved accordingly both practically and in terms of liability/financially.
If this ambiguity exists, then under 63.8 when resolving the ambiguity the Party which did not create the ambiguity is deemed to have allowed the one more favorable to themselves. Therefore that would be no signs, that is what the Employer wants so there is no CE (for a saving). However, if the signs are not part of the technology scope then the Works Info states signs, and if the Employer no longer wants signs then that would be a (negative) compensation event.
If this ambiguity exists, then under 63.8 when resolving the ambiguity the Party which did not create the ambiguity is deemed to have allowed the one more favorable to themselves. Therefore that would be no signs, that is what the Employer wants so there is no CE (for a saving). However, if the signs are not part of the technology scope then the Works Info states signs, and if the Employer no longer wants signs then that would be a (negative) compensation event.