Can dependencies in a critical path method be determined accurately?

Accuracy depends on the instance and perception.

At any given time of analysis or estimation, accuracy is beleived to be maintained. 

I would say yes ... but not always !

We onsultants love the response " it all depends"

and this is one typical situation where the answer really depends on the type of the project, its clartiy, good definition, good insight into how it will be executed, the level of uncertainty surrounding it in full or part, the overall risk classification of the project.

It also depends on the project manager and his/her experience level, knowledge of the subject and the ability to identiify and articulate such dependeencies in the project critical  path!