wire-spec.js

define(['wire!otherSpec'], function(otherSpec) {
    return {
        myModule: {
            extends: { $ref: 'otherSpec.myBaseModule' },
            args: {
                ['argOverrides']
            }
        }
    }
});

Another possible variation:

define({
        otherSpec: {
            wire: 'otherSpec'
        },
        myModule: {
            extends: { $ref: 'otherSpec.myBaseModule' },
            args: {
                ['argOverrides']
            }
        }
});