does GRZ's contract allow them to sell rights to LB without ven approval?

No. Concessions cannot be transferred to third parties without government approval. However the concession is not held by GRZ's Canadian parent but by a wholly owned Venezuelan subsiduary , so it might be possible at least legally.

However this brings up another point. The CVG owns the concession to Las Cristinas, a point many here seem to ignore when they go on about the differences between LC and LB concessions, contracts etc. There is nothing to prevent the government rescinding all concessions including LC and that would leave the CVG without any legal access to LC. It's just taking something out of one pocket and putting it into another, but it certainly would complicate the situation with KRY's contract if they ended up holding a contract with an entity (even if it was government sponsored) that had no concession or rights to the property.

The CVG is broke and could be bankrupted at any time; that's one way to get out of a lot of these promises to pay miners and money losing nationalised industries that they have never actually paid for.

On the Rusoro bid for GRZ, the real winner if it was successful would be the government of Venezuela. Once the concession got into RML's hands (I am sure that Hugo would approve that transfer), then the legal compensation problem goes away.

IMO the main reason that Venezuela has simply sat on the permits for both GRZ and KRY is that they simply don't want to trigger a default on their part and start an ICSID claim process which they would probably lose. By doing nothing they prevent activity and they hope to win by default when the GRZ and KRY simply give up thus losing their claims to damages. They have become impatient (and so have the locals who need jobs) so the RML bid is a quick end run around the problem.

The real questions is why Chavez is so against GRZ and KRY building and operating the mines? If he would have handled the matter in a reasonable manner the mines would be producing now and he would be seeing investment, jobs and income flowing in.

My explanation is that the lower ranked officers wanted personal "sweeteners" in the form of brown paper bags of unmarked bills in order to process the applications, and when those were not forthcoming they simply left the paperwork in the "pending" tray while at the same time inventing "reasons" for their superiors as to why the permits could not be granted. The situation is so entrenched that nobody can talk or move without exposing the whole crooked mess. The Russians are quite used to operating in this environment so they are seen as the way out for the Venezuelans who are involved.