The info in Child and The Family that Flor mentioned is, IMO, very important because above all, Montessori believed that children should be active and participating members in the life of the home. There is some related info about this in Absorbent Mind and The Discovery of the Child. In Absorbent Mind, ch. 9, "The First Days of Life" she exonerates the "Western Custom" of "banishing" the child to a nursery when he should be with the family and discusses different customes of babywearing as well as "prolonging the period of maternal feeding", both of which she discusses in a positive light.
Another point to consider is that Montessori stressed responding to individual differences in needs and aptitudes. She outlined a general structure for identifying universal human sensitive periods and tendencies as well as defining the Absorbent Mind but we apply these theories to the child in a way that respects her individuality. With this in mind, I feel that the Montessori application of bedtime can have some variety in different homes. Every family is a dynamic unit and the child must necessarily learn to accomodate others just as others work to accomodate his needs. This is a learning process, as is normalization, and for every child, he will follow his own unique timetable.
One of the Montessori's "sensitive periods" is important to understand in relation to sleeping. This is the sensitive period for order which guides the child from birth until the age of 3. This period peaks at 2. The child observes and absorbs patterns of activity and familiar objects. It is distressing to the child when order is disturbed. Order in the environment and in the routines of the day help the child to feel secure and to feel trust in the world. To support the child in this stage, the adult should provide a natural, consistent environment including routines and rhythms. To me this translates to having a bedtime that is fairly consistent each night, whether it be 7 or 10, and having a consistent bedtime routine. So, each family can decide for themselves what the daily routine should be. Of course, because the child has absorbed the routine throughout the first 3 years, it may be extremely difficult to change this pattern at 4 or 5 and later. In other words, whatever you set up as a routine for your child (falling asleep on own/falling asleep together and the time for going to bed) in the first 3 years, will be what she is most comfortable with. "The impressions the child's mind receives, and the emotional consequences they provoke, tend to remain permanently registered in it". (Absorbent Mind)
Helping the child to fall asleep on his own (just as we look for ways to help him develop every independence) during this sensitive period can help the child feel secure and confident in his sleep habits. This is the point that the M.Olaf catalogs (S. Stephenson) and "Montessori from the Start" (Lillards) are expressing. I wanted my daughter to develop a healthy attitude towards sleep including the ability to fall asleep on her own. Even as an infant, I would take dd off the breast for her to fall asleep and put her down in a dark quiet room for her little naps. I didn't think that teaching her to depend on me to fall asleep would be healthy in the long run so I started from a very young age giving her the opportunity to fall asleep on her own and then gradually extending this skill (though she did fall asleep nursing many times). When she was about 4 to 12 mths, she was great at napping and falling asleep at night on her own. Interestingly, she became more dependent on me at nap and bed time between the ages of 1 and 2. Now, she goes to bed on her own between 9 and 10 (or with me if I am ready) if she has napped during the day, at 7 or 8 if she hasn't. She is in a transitory stage between napping/not napping so each day we go with the flow. We do sort of cosleeping because she has always come into our bed in the middle of the night. Even this she is gradually outgrowing.