I have checked on this point and the bad news is that the speed has not changed. The difficulty is that Part A is an example of authentic speaking. This means that you are 'in the room' with the practitioner and the patient, listening to a real conversation. As with any real conversation, there are times that the speaker will talk a bit faster or slower. They may vary the pitch of their speech - perhaps speaking a bit softer if they are unsure of what they are saying.
So, how do you prepare for this part of the Listening? You need to listen to as many authentic conversations as possible, trying to listen for the structure of the text. When does the speaker pause? (is it to draw attention to a key point?). Does the speaker's voice go up at the end of the sentence? Remember that if you are listening to Australians speaking, their voices often go up at the end of a sentence. This is more common in female speech. Sometimes it may appear that they are asking a question or sounding unsure but this may not be the case. You need to listen to everything in and around the sentence to be sure.
Talk-back radio is a good opportunity to hear real conversations. They give you the opportunity to develop awareness of how people speak especially how they speak to strangers. Listen and take notes. Identify the words which go together as common phrases. As you become familiar with these phrases, your brain will start 'filling in the missing words'. What I mean is that as you train your brain to listen for key words; the surrounding less important words of the phrase will be filled in for you.
Listening skills are similar to reading skills in that you need to train yourself to pick out /listen for key terms only.
Try to prepare for all 4 skills (reading, writing, listening and speaking) together. I develop packs around a single health topic for this reason. By reading about a topic e.g. skin cancer, you start to build a vocabulary of terms relating to the topic. Then,as you listen to a podcast about skin cancer, for instance,you will recognise the key terms because you have already seen them in print. This is very important as many words when spoken do not resemble the word when it is written.
So, read the word, look up its meaning and check the pronunciation (use any online dictionary which has audio clips for pronunciation). As you hear the word, it is now familiar. A good example of this is the word 'phlegm'. Unless you had read the word and checked the pronunciation, you would have no idea what was being spoken about!
You should also add any phrases which go with your key term. For example, 'cough up' is often heard with 'phlegm'. Carry a small notebook with you and write down phrases or compound words which belong together. This is another way of training your brain to hear only the key terms. Remember that your brain will eventually start to fill in the gaps by itself.