Yosemite Photos can't delete photos from iPhone
In Photos you have an option to "delete items after import" near the imports buttons, in the top right corner



In Photos on the other corner I have "Open photos from this device checked"



Try to keep up to date Yosemite, Itunes and Photos. Also in Itunes when you connect your apple device in the Photos settings uncheck "Sync Photos"



After you have done all this. Restart your computer. and try again.