The vertically integrated Tesla strategy is to use batteries to arbitrage the value of stored energy. This is well described in the Tesla "Master Plan" documents. Solar is a huge part of this.
According to the company filings the solar assets Tesla acquired are still generating revenue at the rates projected during the acquisition.
Well I trust Elon's statements (even the financial statements) as far as I can throw them but can you point out where it says that? I'm searching the 10-K and I don't see solar broken out.
But even if it's true I assume they are including their utility-scale solar and battery packs, which has nothing to do with Solar City: the panels are generic, the customer lists are not residential, they don't use the fancy shingles. Solar City did not help them in any way with these getting or fulfilling these contracts.
According to the company filings the solar assets Tesla acquired are still generating revenue at the rates projected during the acquisition.