eduroam, as a not-for-profit roaming consortium, is in the comfortable position of not having to rely on accurate RADIUS Accounting data.
This is quite fortunate because RADIUS Accounting, even though specified in RFC2866, is very underspecified and has many interoperability issues - especially in a world-wide roaming environment with numerous vendors and firmware versions of WiFi access points, which may all report with RADIUS accounting in a slightly different way. Since it provides no tangible benefit to eduroam operations, RADIUS Accounting is generally frowned upon. For many countries, particularly for European countries, eduroam Operations expects National Roaming Operators to acknowledge and discard Accounting packets destined to an eduroam IdP outside their own national federation; i.e. to confine Accounting, if it is really desired, to their own country.
Some countries do use Accounting information inside their country for various reasons, and eduroam Operations does not interfere with that.
For eduroam SPs, the consequence is that they can safely turn off RADIUS Accounting unless their National Roaming Operator insists on accounting records being sent.
As an eduroam IdP, the consequence is that you may receive accounting records from your own users when they roam to a different hotspot for which RADIUS Accounting has been turned on. Note that the number and content of attributes in the Accounting packets varies greatly due to the underspecification in RFC2866; you can not rely on any single Accounting attribute being present. It is possible, and probably the best option, to simply discard Accounting packets which cannot be correctly understood by your RADIUS server.