I was looking for a wiki page that described the Yahoo provider better, but all I could find was the plug-in download page.

So the Yahoo price data provider is about EoD Daily bars, but it appears to supply on-demand data for intraday bars too for the S&P 500 (^GSPC) as well. Am I correct about that? And when I new bar enters the intraday chart, it automatically updates that chart (on-demand?) for the new bar as well.

I'm asking because I'm trying to avoid paying extra for IQFeed S&P 500 intraday data (SPX.XO) if Yahoo data will work.

According to the WL User Guide > Data > Data Manager > Create New DataSet > Data Providers > Yahoo!

QUOTE:
Always return data with partial bar

When the option is enabled, static data will include the current day's partial bar, and the last bar will be corrected on each update. File > Update Data on Demand must also be enabled.