You can use the AbcImport and AbcExport MEL commands to import and export Alembic files. For example, use the following to export a polygon torus:
AbcExport -j "-frameRange 1 120 -root pTorus1 -file c:/temp/test.abc";
Help for the commands is available in the Script Editor using either AbcExport -h; and AbcImport -h;.
For GPU caches, there is no import command. Instead, you create the gpuCache node and set attributes for cache file name and path. For example:
createNode -n "mine" gpuCache;
setAttr -e -type "string" mine.cacheFileName "dd.abc";
setAttr -e -type "string" mine.cacheGeomPath "|"; // eg the root.