yes, that functionality is supported but the overall workflow hasn't been completely worked out. Here are the steps required:
1. Download data for the area you are working in.
2. Extract the attributes from the downloaded data into which you would like to map your data. Essentially you are preparing a target for the field mapping in step 5.
3. Create a feature describing your bounding box of your existing BLM data.
4. Use the feature from step 3 in the erase tool to cut out the "old" OSM data.
5. Use the append tool to copy your BLM data into the appropriate OSM feature class. At this point be sure to set up the appropriate field mapping from your data and match them into the normalized OSM attributes from step 2.
6. Run the "Combine OSM Attributes" tool to merge the normalized fields into the collective OSM tag field.
7. Upload the changes.
As a general recommendation if you are looking at the data as "raw" feature classes in ArcMap you should use a definition query of "supportingElement = 'no'" and then work against those layers. You as the user shouldn't care about geometry primitives of
OSM nodes and ways, but focus on the map features presented as points, lines, and polygons.