Hi there.
HMP does not define specifically any geolocation services as a part of its API, but it provides means to set and read any arbitrary SIP headers and MIME bodies, where appropriate, in supported SIP messages.
From the message list in RFC5491 HMP does not support SIP MESSAGE and SIP PUBLISH requests, which may be OK for most applications. More serious limitation is that there is no HMP support for 424 (Bad Location Information) response currently, even though more generic 400 Bad Request can be used with HMP.