Do GORM / GMongo wrap collections to accept Maps? (Grails / GMongo internals.)

Question

I'm working with Grails Mongo domain objects and I've noticed that I get very different behavior with the following two ways to access a collection:

c1: collection name is known at compile time:

def c1 = MyDomainClass.collection

c2: collection name is only known at runtime

def c2 = AnyDomainClass.collection.DB.getCollection(collectionName)

c1 and c2 have the same class, but behave differently!

Both c1 and c2 have the class com.mongodb.DBApiLayer$MyCollection but they behave differently.

Specifically, c1 supports "friendly" interactions like passing Maps directly to GMongo methods, e.g.

c1.find([tag:'spicy']).sort([created:1])

Whereas c2 only works with DBObject parameters like:

c2.find(new BasicDBObject([tag:'spicy'])).sort(new BasicDBObject([created:1]))

I prefer the syntax in #1, and I would like to be able to use that syntax with objects even when I don't know the collection at compile time. In other words, I want to be able to dynamically access collections (which I can do with #2), but using the "friendly" syntax from #1.

My questions are:

1. How are c1 and c2 different?
2. How can I instantiate collections that behave like c1 when the collection is unknown at compile time?
3. At what layer of the Grails/GORM/GMongo stack are objects wrapped to support map-to-DBObject conversions, and how is this done?