DALI bus power supply requirements
Assuming the DALI device doesn't have an integrated bus power supply - that is to say, it is not providing the voltage on the DALI bus, there are two options. If it is powered by another input (not just the DALI one), usually a mains input, like an LED driver is, then it is subject to the limit of drawing 2mA from the bus. That limit applies over the range of bus voltages and other conditions, so you will probably find devices drawing 1.5mA at 16V, but don't rely on it being much less than 2mA. 

If it is powered by the DALI bus then it can draw any current up to the 250mA limit whilst in the non-transmitting state (not pulling the line low). This option is typically used for occupancy sensors, light sensors, switch input devices and similar. The current rating must be stated by the manufacturer and as a system designer you have to ensure the sum of the currents in the non-transmitting state is less than your power supply current limit (the voltage remains high).

You can have just one bus power supply which keeps things easy, as a separate device from the other products (sensors, control gear etc) or multiple power supplies as long as they meet the overall requirements together, total current limit below 250mA. Or you can integrate the bus power supply into the controller (sensor, control plate etc) or into the control gear (LED drivers etc).

Wherever the power supply is located, there is also a minimum current limit of 8mA required by the standard.

So, no, each device is not allowed to consume 4mA from the bus unless it is classed as bus powered and has no other power terminals, and yes, a 10mA supply is acceptable.