Myofibrillar protein synthesis ie. Creating new muscle tissue does have an upper limit, and once past this limit any excess calories will no longer be used towards MPS.
However, a number of factors will affect this limit and therefore the amount of calories that can be utilised for MPS, for one person this may only be 50, for another it may be 200 or 400. Without looking at the literature I cannot say for certain what the upper limit would be.
Some of the factors worth noting are; nutrition (protein, carbs and fats, micronutrients, specific amino acids such as leucine), training (type, volume, intensity, frequency), drugs (specific compounds, doseage), internal stress (ie. disease, fatigue, recovery etc.)