The Maximo 7.1.1.6 base services fix pack provides the Maximo Integration Framework with functionality to include and receive attachments as part of an XML message payload.
On the outbound side:

1. Add DOCLINKS to your integration object structure
2. Include the non-persistent attribute DOCUMENTDATA. This attribute will hold the actual data of your attachment encrypted in base-64
3. In your outbound XML payload you MUST include:
   a. <ADDINFO>1</ADDINFO>
   b. <UPLOAD>1</UPLOAD>
   c. <URLNAME>physical path + file name + extension</URLNAME>

Step 3 is very important. It insures that Maximo generates the new attachment file name correctly and ties it to the URL in the new DOCINFO object.
On the inbound side:

1. Add DOCLINKS to your integration object structure
2. In the “Inbound Setting Restrictions” override and unrestrict “ADDINFO” and “URLNAME”

I recently completed this as part of an integration from one Maximo system to another. I was moving an SR along with its work log entries and attachments.
Sample XML file
Provided in this technote is a Purchase Order xml file that includes a text file as an attachment. Inclusion of the DOCLINKS object as a child of the PO object in the MXPO object structure is required before attempting importing the sample xml file.