Ecamm's marker feature creates a text file containing time stamps and marker text. Although Adobe Premiere's marker import feature is very limited, it's possible to import Ecamm's markers using a free extension.
(Don't worry, you'll only have to follow the first four steps once!)
Download the free MarkerBox extension.
Install using the steps on the MarkerBox website.
For newer versions of Premiere, when following the steps in the Trusting the Extension section, also run this Terminal command:
defaults write com.adobe.CSXS.11 PlayerDebugMode 1
Quit and re-open Adobe Premiere Pro. You should now see a new MarkerBox extension listed in Extensions sub-menu in the Window menu at the top of the screen. Pick it to open MarkerBox.
In the MarkerBox window, use Paste from the Edit menu to paste the markers, and then click the Import from text area button.