Yes, there is a mystical aspect of Tibetan Buddhism but we must not confuse this for the real practice. If you meet any of the highest lamas who are known to be very powerful, they are also always very humble and they will never talk about the visions they see, talk about their conversations with the deities or openly display any of their powers. Like what others have said before, you need to ask why you want to have these powers to converse with deities? There are many, many methods for practicing the Dharma clearly and effectively and well without having to converse directly with the deities. In fact, talking to deities at this time may not be beneficial for us - it could just make us even more arrogant and puffed up,or we get so carried away by the mystical side that we start to neglect the true essence of the teachings which is karma, the 4 noble truths, mind transformation teachings, compassion and developing wisdom.
I had the fortune to meet several very great lamas. They never display or talk about their attainments openly. What makes them so well loved - they have huge followings all over the world, is not because they can do "magic tricks", but because of their tremendous hard work, their very obvious compassion and kindness for others, their generosity. I often think that being truly kind is a greater miracle than so-called "miracles" like controlling the weather etc. What is the point of having these mystical powers if you are still a bad person, with negative thoughts, negative habits and who does negative things to others?