Here is what I found:
phase 0 is about PreparePreferenceMatrixJob and it has 3 hadoop jobs:
PreparePreferenceMatrixJob-ItemIDIndexMapper-Reducer
PreparePreferenceMatrixJob-ToItemPrefsMapper-Reducer
PreparePreferenceMatrixJob-ToItemVectorsMapper-Reducer
phase 1 is about RowSimilarityJob and it has 3 jobs:
RowSimilarityJob-VectorNormMapper-Reducer
RowSimilarityJob-CooccurrencesMapper-Reducer
RowSimilarityJob-UnsymmetrifyMapper-Reducer
phase 2 is about RecommenderJob and it has 3 jobs:
RecommenderJob-SimilarityMatrixRowWrapperMapper-Reducer
RecommenderJob-UserVectorSplitterMapper-Reducer
RecommenderJob-Mapper-Reducer
phase 3 is the last one and it has only one job:
RecommenderJob-PartialMultiplyMapper-Reducer
Also output from phase 1 here in RecommenderJob class is exactly the same as the output from phase 0 and 1 of ItemSimilarityJob (but the temp directory names are different).