Is this a workable UnitOfWork with Repository pattern design?
The UoW pattern has a couple of properties. The UoW will:


track changes to entities, wether that be adding, removing or updating.
coordinate the persisting of these changes in one atomic action. Which also means rolling back if an error occurs.


Since you're using EF, you don't have to implement this stuff, it's done for you. The ObjectContext is actually the UoW object. So unless you plan to switch out Persistence frameworks later on, any additional abstraction will be wasted effort.

I'm guessing you want to make sure your domain isn't aware of how it's persisted. Your domain should only know of the repository interfaces. The repository interfaces are actually part of your domain. The repository implementation though, is part of the persistance layer.

The repository implementation looks OK. I'm only curious about FindByFilter; if you're returning an IQueryable&lt;T&gt; object, you're saying you can query it. OTOH the FindByFilter function already takes an Expression&lt;Func&lt;T, bool&gt;&gt; filter parameter. I'd pick one of the two like the following:

public IEnumerable&lt;T&gt; FindByFilter(Expression&lt;Func&lt;T, bool&gt;&gt; filter)
{
    //
}


or 

public IQueryable&lt;T&gt; FindAll()
{
    //
}


Hope this helps.