Si, usando Streams o directamente asignando strings:
Código Delphi
[-]
uses
System.SysUtils,
System.Classes,
Xml.XMLIntf,
Xml.XMLDoc;
procedure Main;
var
xml: IXMLDocument;
Stream: TMemoryStream;
StringStream: TStringStream;
begin
xml := TXMLDocument.Create(nil);
xml.LoadFromStream(Stream);
xml.LoadFromStream(Stream, TXMLEncodingType.)
StringStream := TStringStream.Create;
idhttp1.Get('blablabla', StringStream);
xml := LoadXMLDocument(StringStream.DataString);
xml := TXMLDocument.Create(nil);
xml.XML := StringStream.DataString;
end;