They are both being groomed by redbull, so they are doing the mid-season switcharoo. It ensures they both get a taste of an F1 weekend.
And onto the points tallys you mentioned Renaultfan, Alguersuari is doing the full season with Carlin. Hartley was only doing the first few races with ?Tech 1? as something to do until the F3 Euroseries kicked off. Brendon is the real deal too!