No. The Tesla software will not allow grid charging Powerwalls if paired with solar. This is done in order to comply with the 30% Investment Tax Credit, which requires residential storage systems to charge 100% from on-site renewable energy in order to qualify for the credit.
Some people have proposed that they should be able to waive the requirement if they don't take the tax credit, but I've never heard of Tesla allowing it. They only way I know of to charge from the grid in the USA is to install a standalone Powerwall system that does not have solar.