It is true that taxis can get into the areas reserved for public transport, and for the elderly or disabled this might be a solution. The prices are official and are measured with a taximeter, you cannot haggle. In addition, taxis don't usually stop in the street in Pamplona, so if you raise your hand they will probably wave back, but not stop. The usual thing is to get them on their ranks or call to 948 23 23 00.