Time to first fix with latest firmware

What is the typical time to first fix using the latest u-blox firmware with good quality antennas.

Is there a parameter in the base data stream that identifies the most current solution available
( single, float or fixed)?

u-blox announces a convergence time of 2 minutes. Usually we observe convergence times of about 3-5 minutes. Convergence time starts once base is emitting differential data.

Base data stream does not contain fix information, only rover does.