Are they exactly 32bits for a 32-bit CPU?
If it is a 32-bit CPU I would expect the width of the data bus to be 32 bits. In addition, I would expect the size of the address bus to be 32 bits. However, you cannot count on that being true. For example, the 8088 was sold as a 16-bit CPU but it had a 8 bit path to memory.
In summary, they usually are 32 bits but they might not be.