This paper recently published in Canadian Journal of School Psychology shows that reading fluency intervention in French improved English reading skills for Grade 3 students in a French immersion program. The full paper can be viewed here: Archambault et al author version
Archambault, C., Mercer, S. H., Cheng, M. P., & Saqui, S. (in press). Lire en Français: Cross-linguistic effects of reading fluency interventions in French immersion programs. Canadian Journal of School Psychology. doi:10.1177/0829573518757790