The AnXI reforms were part of a wider artillery reform initiated in 1803. The organisation of batteries and personell was changed, as was manufature, education etc. This is a point not mentioned in most studies of AnXI material.
By 1805 the changes had been modified again.
The siege guns were used in numbers in 1812, numbers were used as well 1803-1804, as well as in Spain. The Gribeauval guns were only used in Spain as captured ammunition could be used, given that the Spanish used Gribeauval guns. I believe I sent you a copy of my notes on the siege guns and use of Gribeauval guns in Spain.