Yes, it is possible to share the same access code between operators. However, a lot of other call accounting systems do not take care of this feature.
In some countries, it is very common to have multiple lines from different telecom operators within the office. To complicate matters further, all the operators may use the same code for IDD/STD/Toll access.
For example, Operator A uses 001 as the international access code and operator B also uses 001 for the international access code. The difference between these two operators lies in the rates that are being charged.
Given the scenario that you have line 1 (CO1) from Operator A and line 2 (CO2) from operator B, you can actually specify in Call Accounting Mate that line 1 uses Operator A rates by default, and line 2 uses Operator B rates by default. This can be easily done with Call Accounting Mate without any hassle.