Question About Multi-Language and Multi-Speaker Performance

I see that it's possible to train both the variance and acoustic models with multiple languages and multiple speakers. I have a few questions: 1. In a `multi-dictionary` or `multi-language` setup, does the performance in one language **affect** the others? 2. From my experiments with `multi-speaker` models, it seems that speakers with **shorter training data** tend to be influenced by other voices with **longer training data**, especially when the generated pitch goes beyond their original training range. Is this expected behavior? Also, is there any prior evaluation or research on multi-speaker and multi-language performance?