One should be absolutely careful to misunderstand the whole context. Where one has integrated a meditative consciousness, then anytime is the time for meditation. In fact, whether one does something or does nothing - if meditation becomes as natural as your own breath, then it is going to blossom in your experience just as a lotus emanates it's fragrance out of it's own nature. Meditation is not something that is to be set aside as some kind of practice for an hour or two, but it is something that is to be flowing throughout the whole movement of life itself from moment to moment. Although one may sit for meditation, after one's sitting one's meditation should continue - so that whatever arises in your experience, you can remain a witness in the present without becoming identified. It requires some effort in the beginning, not for meditation, but to weed out the hindrances for meditation, because the mind just simply wants to work according to it's conditioning. But eventually, the method becomes methodless, the effort dissolves into the effortless - and the spirit of meditation becomes choiceless.
The reason why Brahma Muhurta has been often recommended as a time which is helpful for meditation is because that is a time during the day when your nervous system functions in a way which can be more supportive for entering meditation, as well as certain psychological tendencies are there which assist one's entry into meditation. At the level of the subtle energies of the body, the sushumna nadi, the central channel along the spinal cord, is active - which is helpful in various different ways. If you are practicing such methods as asana or pranayam at this time, it will help a thorough purification of the nadis. If you are working on awakening the Kundalini, then too, the kinds of energies which are working at this time are very supportive for awakening Kundalini. If you are using this time just for sitting meditation - then too it can be of help. In general - it can be tremendously supportive for sadhana. But I want to make it clear that just because you are practicing at Brahma Muhurta- that does not necessarily mean that your sadhana will be effective. Because whether one's practice is going to be assisting you towards your liberation or not has little to do with such superficialities as what time of the day you are practicing. If there is a certain inner atmosphere where you are absolutely fresh, open and receptive, without being argumentative to the process, with a great willingness, then anytime is the right time for practice. If there is even a single moment of your own naturalness, then this far surpasses even infinite mechanical training. One's liberation has little to do with what you do outside of you, and far more to do with what you do within yourself. All of those methods of trying to use external means are just different ways to assist an inner process, and they should be understood as such. If you do not understand this and start clinging to these external methods, then one has missed the essential matter.