There are certainly ways of conversion, but not really "standardised" ones. In my university, the admissions office is very apt at these comparisons, they have over the years collected large tables how to convert grading schemes as well as academic credit points from all around the world into our local Swedish system.
Of course, this is only one half of the medallion - knowing that an "A" in a specific system usually refers to "85% or more of total credits" is good, but does not tell you how hard it is to get an A and what percentile of students usually gets an A or better. This is a much more difficult to answer question, since this will rarely be officially documented, and answers will be highly local to individual universities, programs, or even courses.
This is one of the reasons why some universities have started providing "rankings" of candidates upon graduation in addition to their grades (e.g., when my wife graduated her degree stated that her grades were among the top-n percentile of students in this year and program).
To answer your question:
How can grades from these and other countries be effectively compared when considering applications for academic positions?
Basically, you can't. I'm not sure you should even compare candidates based on grades from the same country, and when you throw in different grading schemes and academic tradition I believe it becomes effectively a fool's errant trying to assess if a 1.3 from country A is better than a A- from country B.