I have opened three files, one of which has different eol than the others but there's no indication of this in pluma. They can be edited and saved without problem and they preserve their original eol format but I would feel saver if there was at least some indication like in vim there is "[dos]" in the status line.
As a bonus we could have a conversion functionality some day.
Midnight Commander supports this feature, as well, and it is a very very nice feature.
There is https://code.google.com/p/gedit-line-ending-style-plugin/
Which you can modify so it can be used with pluma.